Group 2 Exam Pack

Home , Strontium hydroxide, Strontium nitrate, Strontium oxide, Strontium sulfate

Name: ______Group 2 exam pack

Class: ______

Date: ______

Time: 306 minutes

Marks: 259 marks

Comments:

Page 1 of 71 Q1. An aqueous solution Y is known to contain one type of group 2 metal ion and one type of negative ion.

Aqueous solutions of sulfuric acid and magnesium nitrate are added to separate samples of solution Y. The observations are shown in the table.

Solution added Observation with solution Y Sulfuric acid A white precipitate forms

Magnesium nitrate A white precipitate forms

(a) Suggest the identity of the group 2 metal ion present in solution Y.

Write an ionic equation, including state symbols, for the reaction that takes place when sulfuric acid is added to solution Y.

Group 2 metal ion ______

Ionic equation ______(2)

(b) Suggest the identity of the negative ion present in solution Y.

Write an ionic equation, including state symbols, for the reaction that takes place when magnesium nitrate is added to solution Y.

Negative ion ______

Ionic equation ______(2) (Total 4 marks)

Q2. This question is about ion testing.

(a) Describe how a student could distinguish between aqueous solutions of potassium nitrate, KNO3, and potassium sulfate, K2SO4, using one simple test-tube reaction.

Reagent ______

Observation with KNO3(aq) ______

______

Observation with K2SO4(aq) ______

______(3)

(b) Describe how a student could distinguish between aqueous solutions of magnesium chloride, MgCl2, and aluminium chloride, AlCl3, using one simple test-tube reaction.

Page 2 of 71 Reagent ______

Observation with MgCl2(aq) ______

______

Observation with AlCl3(aq) ______

______(3) (Total 6 marks)

Q3. A sample of strontium ore is known to contain strontium oxide, strontium carbonate and some inert impurities. To determine the mass of strontium carbonate present, a student weighed a sample of the solid ore and then heated it in a crucible for 5 minutes. The sample was allowed to cool and then reweighed. This heating, cooling and reweighing was carried out three times.

The results are set out in the table.

Mass of crucible / g 9.85

Mass of crucible and ore sample / g 16.11

Mass of crucible and sample after first 14.66 heating / g

Mass of crucible and sample after second 14.58 heating / g

Mass of crucible and sample after third 14.58 heating / g

(a) When strontium carbonate is heated it decomposes according to the following equation.

SrCO3 SrO + CO2

Give a reason why the mass of the solid⟶ sample changed during the experiment.

______

______(1)

(b) Use the data in the table to calculate the mass of strontium carbonate in the original ore sample. Give your answer to an appropriate precision.

Page 3 of 71 Mass of strontium carbonate = ___ g (5)

Calculate the percentage error in the initial mass of ore used.

Percentage error = ______% (1)

(d) The mass of inert impurities in the sample was 347 mg.

Deduce the mass of SrO in the sample and justify any assumption made in calculating your answer. (If you have been unable to answer part (b), assume the mass of strontium carbonate was 4.85 g. This is not the correct answer.)

Mass of SrO = ______

______

______(2)

(e) Strontium metal can be extracted by heating strontium oxide with aluminium metal.

In this reaction, strontium vapour and solid aluminium oxide are formed.

Write an equation for the reaction and state the role of the aluminium in the process. Explain why strontium forms a vapour but aluminium oxide is formed as a solid.

Equation

______

Role of aluminium ______

______

Explanation ______

______

Page 4 of 71 ______(5) (Total 14 marks)

Q4. This question is about the chemistry of some Group 2 elements.

(a) Write an equation for the reaction of calcium with water at 25 °C and predict a possible value for the pH of the solution formed.

Equation

______

pH ______(2)

(b) State the trend in solubility, in water, of the Group 2 sulfates from magnesium to barium.

______(1)

Reagent ______

Equation

______(2)

(d) Explain why the melting point of calcium sulfate is high.

______

______(2) (Total 7 marks)

Q5. This question is about the elements in Group 2 and their compounds.

Page 5 of 71 (a) Use the Periodic Table to deduce the full electron configuration of calcium.

______(1)

(b) Write an ionic equation, with state symbols, to show the reaction of calcium with an excess of water.

______(1)

(d) Write an equation to show the process that occurs when the first ionisation energy of calcium is measured.

______(1)

(e) State and explain the trend in the first ionisation energies of the elements in Group 2 from magnesium to barium.

Trend ______

Explanation ______

______

______(3) (Total 7 marks)

Q6. The table below shows observations of changes from some test-tube reactions of aqueous solutions of compounds Q, R and S with five different aqueous reagents. The initial colours of the solutions are not given.

BaCl2 + HCl AgNO3 + NaOH Na2CO3 HCl (conc) HNO3

no change pale cream white white no change Q observed precipitate precipitate precipitate observed

no change white white white no change R observd precipitate precipitate, precipitate, observed dissolves in bubbles of a

Page 6 of 71 excess of gas NaOH

brown white no change brown precipitate, yellow S precipitate observed precipitate bubbles of a solution gas

(a) Identify each of compounds Q, R and S. You are not required to explain your answers.

Identity of Q ______

______

Identity of R ______

______

Identity of S ______

______(6)

(b) Write ionic equations for each of the positive observations with S.

______

______(4) (Total 10 marks)

Q7. An experiment to investigate enthalpy was carried out with calcium instead of magnesium, and with 2.0 mol dm–3 sulfuric acid instead of 2.0 mol dm–3 hydrochloric acid. Both acids were in excess. At first the reaction of calcium with sulfuric acid was faster than the reaction of magnesium with hydrochloric acid. However, the reaction of calcium with sulfuric acid soon stopped even though some calcium remained. A white solid had formed.

Page 7 of 71 (a) Suggest two reasons why the reaction was faster at first with calcium and sulfuric acid than with magnesium and hydrochloric acid.

Reason 1 ______

______

Reason 2 ______

______(2)

(b) Identify the white solid and write an equation for its formation in this reaction.

Explain why the reaction of calcium with sulfuric acid stopped even though some calcium remained.

Identity of white solid ______

Equation ______

Explanation ______

______

______(3) (Total 5 marks)

Q8. A student was given a powder made from a mixture of anhydrous barium chloride and anhydrous magnesium chloride. The student dissolved 1.056 g of the powder in water in a conical flask and added an excess of sulfuric acid. A white precipitate formed and was filtered off, washed and dried. The mass of this solid was 0.764 g.

Identify the white precipitate and calculate the percentage, by mass, of magnesium chloride in the powder.

______

Page 8 of 71 ______

______

______(Total 4 marks)

Q9. Which of these decreases down Group 2?

A First ionisation energy

B Atomic radius

C Number of protons

D Reactivity with water (Total 1 mark)

Q10. Sulfur dioxide (SO2) is produced when some fossil fuels are burned.

Which of the following statements is true?

A Sulfur dioxide can be removed from waste gases in a power station by an acid-base reaction with calcium oxide.

B Sulfur dioxide is insoluble in water.

C Sulfur dioxide is a basic oxide.

D Sulfur dioxide is an ionic compound. (Total 1 mark)

Q11. This question is about the Group 2 metals and their compounds.

(a) Explain why the first ionisation energy of barium is less than the first ionisation energy of calcium.

______

______(2)

(b) Magnesium reacts readily with steam.

Page 9 of 71 State two observations you would make when magnesium reacts with steam. Write an equation for the reaction.

Observation 1______

______

Observation 2______

______

Equation______(3)

(c) Explain why different observations are made when aqueous barium chloride is added separately to aqueous magnesium sulfate and to aqueous magnesium nitrate.

Write the simplest ionic equation, including state symbols, for any reaction that occurs.

Explanation ______

______

Equation______(2) (Total 7 marks)

Q12. The following pairs of compounds can be distinguished by simple test−tube reactions.

For each pair of compounds, give a reagent (or combination of reagents) that, when added separately to each compound, could be used to distinguish between them. State what is observed in each case.

(a) Butan−2−ol and 2−methylpropan−2−ol

Reagent ______

Observation with butan−2−ol

______

Observation with 2−methylpropan−2−ol

______

Page 10 of 71 (3)

(b) Propane and propene

Reagent ______

Observation with propane

______

Observation with propene

______

______(3)

Reagent ______

Observation with aqueous silver nitrate

______

Observation with aqueous sodium nitrate

______

______(3)

(d) Aqueous magnesium chloride and aqueous barium chloride

Reagent ______

Observation with aqueous magnesium chloride

______

Observation with aqueous barium chloride

______

______(3) (Total 12 marks)

Q13. The elements in Group 2 from Mg to Ba can be used to show the trends in properties down a group in the Periodic Table.

Page 11 of 71 (a) State the trend in atomic radius for atoms of the elements down Group 2 from Mg to Ba Give a reason for this trend.

Trend______

Reason ______

______

______(2)

(b) The Group 2 elements react with water.

(i) State the trend in reactivity with water of the elements down Group 2 from Mg to Ba

______(1)

(ii) Write an equation for the reaction of strontium with water.

______(1)

______(1) (Total 5 marks)

Q14. Zinc is similar to Group 2 metals and forms compounds containing Zn2+ ions.

Write an equation for the thermal decomposition of zinc carbonate to zinc oxide.

Calculate the percentage atom economy for the formation of zinc oxide from zinc carbonate in this reaction.

Equation ______

______

Percentage atom economy ______

______

Page 12 of 71 (Total 3 marks)

Q15. A laboratory technician discovered four badly−labelled bottles, each containing one pure white solid. Each bottle contained a compound of a different Group 2 metal (magnesium, calcium, strontium and barium).

Some tests were carried out on the solids or, if the compound was soluble, on the aqueous solution. The results are given in the table.

Test Compound 1 Compound 2 Compound 3 Compound 4

Added to water Dissolves Insoluble Dissolves Dissolves

Gives off Solution Solution or solid Solution carbon dioxide Solution remains added to remains gas and a remains colourless and HCl(aq) colourless colourless colourless heat released solution forms

Solution or solid Solution gives a Solution gives a Solid remains Solution has no added to white slight white insoluble visible change NaOH(aq) precipitate precipitate

Gives off Solution slowly Solution or solid Solution forms Solution has no carbon dioxide forms a slight added to a white visible change gas and a white white H2SO4(aq) precipitate solid remains precipitate

(a) One of the bottles has a very faint label that could be read as ‘Magnesium Sulfate’.

Use the information in the table to deduce which one of the four compounds is magnesium sulfate and explain your answer.

Compound ______

Explanation ______

______

______(3)

(b) The bottle containing Compound 2 has a ‘TOXIC’ hazard symbol.

Use the information in the table to identify Compound 2.

Explain both observations in the reaction with H2SO4(aq).

Identity of Compound 2 ______

Page 13 of 71 Explanation ______

______

______(3)

Give an equation for the reaction of strontium hydroxide with sulfuric acid.

Compound ______

______

Equation ______

______(2) (Total 8 marks)

Q16. Calcium hydroxide is slightly soluble in water at room temperature. As the temperature rises, the solubility decreases. When the maximum amount of solid has dissolved at a particular temperature the solution is said to be saturated.

In an experiment, the solubility of calcium hydroxide was measured over a range of temperatures. The results are shown in the graph.

Page 14 of 71

(a) Use data from the graph to calculate the concentration, in mol dm−3, of a saturated solution of calcium hydroxide at 30 °C. Give your answer to 3 significant figures.

Show your working.

______

______(3)

(b) You are given a sample of saturated calcium hydroxide solution. Outline the practical steps that you would take to determine the solubility of calcium hydroxide in this solution.

______

Page 15 of 71 ______

______

______(3) (Total 6 marks)

Q17. There are many uses for Group 2 metals and their compounds.

(a) State a medical use of barium sulfate. State why this use of barium sulfate is safe, given that solutions containing barium ions are poisonous.

Use ______

Why this use is safe ______

______

______(2)

(b) Magnesium hydroxide is used in antacid preparations to neutralise excess stomach acid.

Write an equation for the reaction of magnesium hydroxide with hydrochloric acid.

______(1)

State why magnesium hydroxide solution could not be used for this purpose.

______

______(1)

(d) Magnesium metal is used to make titanium from titanium(IV) chloride.

Write an equation for this reaction of magnesium with titanium(IV) chloride.

______(1)

(e) Magnesium burns with a bright white light and is used in flares and fireworks.

Use your knowledge of the reactions of Group 2 metals with water to explain why water should not be used to put out a fire in which magnesium metal is burning.

______

Page 16 of 71 ______

______

(Extra space) ______

______(2) (Total 7 marks)

Q18. (a) Strontium chloride is used in toothpaste for sensitive teeth. Both strontium carbonate and strontium sulfate are white solids that are insoluble in water.

(i) Write an equation for the reaction between strontium chloride solution and sodium sulfate solution. Include state symbols in your equation.

______(1)

(ii) Strontium carbonate reacts with nitric acid to produce a solution of strontium nitrate. Strontium sulfate does not react with nitric acid.

Describe briefly how you could obtain strontium sulfate from a mixture of strontium carbonate and strontium sulfate. You are not required to describe the purification of the strontium sulfate.

______

______(2)

(b) A solution of magnesium sulfate is sometimes given as first aid to someone who has swallowed barium chloride.

Explain why drinking magnesium sulfate solution is effective in the treatment of barium poisoning.

______

______(1)

(c) Medicines for the treatment of nervous disorders often contain calcium bromide. Silver nitrate, acidified with dilute nitric acid, can be used together with another

Page 17 of 71 reagent to test for the presence of bromide ions in a solution of a medicine.

Describe briefly how you would carry out this test and state what you would observe.

______

______(3) (Total 7 marks)

Q19. (a) Anhydrous strontium chloride is not used in toothpaste because it absorbs water from the atmosphere. The hexahydrate, SrCl2.6H2O, is preferred.

A chemist was asked to determine the purity of a sample of strontium chloride hexahydrate. The chemist weighed out 2.25 g of the sample and added it to 100 cm3 of water. The mixture was warmed and stirred for several minutes to dissolve all of the strontium chloride in the sample. The mixture was then filtered into a conical flask. An excess of silver nitrate solution was added to the flask and the contents swirled for 1 minute to make sure that the precipitation was complete.

The silver chloride precipitate was separated from the mixture by filtration. The precipitate was washed several times with deionised water and dried carefully. The chemist weighed the dry precipitate and recorded a mass of 1.55 g.

(i) Calculate the amount, in moles, of AgCl in 1.55 g of silver chloride (Mr = 143.4).

______(1)

(ii) The equation for the reaction between strontium chloride and silver nitrate is

SrCl2 + 2AgNO3 2AgCl + Sr(NO3)2

Use your answer from part (i) and this equation to calculate the amount, in moles, of SrCl2 needed to form 1.55 g of silver chloride.

______

______(1)

(iii) Use data from the Periodic Table to calculate the Mr of strontium chloride hexahydrate. Give your answer to 1 decimal place.

______

______(1)

Page 18 of 71 (iv) Use your answers from parts (a)(ii) and (a)(iii) to calculate the percentage by mass of strontium chloride hexahydrate in the sample. Show your working. Give your answer to the appropriate precision.

______

______(2)

(v) Several steps in the practical procedure were designed to ensure an accurate value for the percentage by mass of strontium chloride hexahydrate in the sample.

1 Explain why the solution of strontium chloride was filtered to remove insoluble impurities before the addition of silver nitrate.

______

______(1)

2 Explain why the precipitate of silver chloride was washed several times with deionised water.

______

______(1)

(b) Magnesium hydroxide and magnesium carbonate are used to reduce acidity in the stomach. Magnesium hydroxide can be prepared by the reaction of solutions of magnesium chloride and sodium hydroxide.

(i) Write the simplest ionic equation for the reaction that occurs between magnesium chloride and sodium hydroxide. Include state symbols in your equation.

______(1)

(ii) Other than cost, explain one advantage of using magnesium hydroxide rather than magnesium carbonate to reduce acidity in the stomach.

______

______(1)

(c) Calcium ethanoate, (CH3COO)2Ca, is used in the treatment of kidney disease. Thermal decomposition of calcium ethanoate under certain conditions gives propanone and one other product.

Write an equation for the thermal decomposition of calcium ethanoate.

Page 19 of 71 ______(1)

(d) Salts containing the chromate(VI) ion are usually yellow in colour. Calcium chromate(VI) is soluble in water. Strontium chromate(VI) is insoluble in water, but will dissolve in a solution of ethanoic acid. Barium chromate(VI) is insoluble in water and is also insoluble in a solution of ethanoic acid.

Describe a series of tests using solutions of sodium chromate(VI) and ethanoic acid that would allow you to distinguish between separate solutions of calcium chloride, strontium chloride and barium chloride. State what you would observe in each test.

______

______(3)

(e) The strontium salt of ranelic acid is used to promote bone growth. Analysis of a pure sample of ranelic acid showed that it contained 42.09% of carbon, 2.92% of hydrogen, 8.18% of nitrogen, 37.42% of oxygen and 9.39% of sulfur by mass.

Use these data to calculate the empirical formula of ranelic acid. Show your working.

______

______(2) (Total 15 marks)

Q20. A student investigated how the initial rate of reaction between sulfuric acid and magnesium at 20 °C is affected by the concentration of the acid.

The equation for the reaction is

Page 20 of 71 H2SO4(aq) + Mg(s) MgSO4(aq) + H2(g)

(a) The student made measurements every 20 seconds for 5 minutes. The student then repeated the experiment using double the concentration of sulfuric acid.

State a measurement that the student should make every 20 seconds. Identify the apparatus that the student could use to make this measurement.

______

______(2)

(b) State one condition, other than temperature and pressure, that would need to be kept constant in this investigation.

______

______(1)

(c) When the student had finished the investigation, an excess of sodium hydroxide solution was added to the reaction mixture. This was to neutralise any unreacted sulfuric acid. The student found that a further reaction took place, producing magnesium hydroxide.

(i) Draw a diagram to show how the student could separate the magnesium hydroxide from the reaction mixture.

(2)

(ii) Suggest one method the student could use for removing soluble impurities from the sample of magnesium hydroxide that has been separated.

______

Page 21 of 71 (1) (Total 6 marks)

Q21. Group 2 metals and their compounds are used commercially in a variety of processes.

(a) Strontium is extracted from strontium oxide (SrO) by heating a mixture of powdered strontium oxide and powdered aluminium.

Consider these standard enthalpies of formation.

SrO(s) Al2O3(s)

ϴ −1 ΔHf / kJ mol – 590 – 1669

3SrO(s) + 2Al(s) 3Sr(s) + Al2O3(s)

Use these data and the equation to calculate the standard enthalpy change for this extraction of strontium.

The use of powdered strontium oxide and powdered aluminium increases the surface area of the reactants. Suggest one reason why this increases the reaction rate.

Suggest one major reason why this method of extracting strontium is expensive.

______

______(5)

(b) Explain why calcium has a higher melting point than strontium.

______

Page 22 of 71 ______

______

______(2)

(c) Magnesium is used in fireworks. It reacts rapidly with oxygen, burning with a bright white light. Magnesium reacts slowly with cold water.

Write an equation for the reaction of magnesium with oxygen.

Write an equation for the reaction of magnesium with cold water.

Give a medical use for the magnesium compound formed in the reaction of magnesium with cold water.

______

______(3) (Total 10 marks)

Q22. (a) In an investigation of the rate of reaction between hydrochloric acid and pure magnesium, a student obtained the following curve.

Page 23 of 71 The reaction of magnesium with dilute hydrochloric acid is exothermic.

Use your understanding of collision theory to explain why the student did not obtain a straight line.

______

______(3)

(b) The magnesium used in a laboratory experiment was supplied as a ribbon. The ribbon was stored in an open plastic bag exposed to the air.

Explain why it is important to clean the surface of this magnesium ribbon when investigating the rate of its reaction with hydrochloric acid.

______

______(2)

(c) Magnesium ribbon reacts with hot water. Heated magnesium ribbon reacts with steam. State two differences between these reactions.

Difference 1 ______

______

Difference 2 ______

______(2)

(d) Pure magnesium reacts completely with an excess of dilute sulfuric acid. The reaction of pure calcium with an excess of dilute sulfuric acid is very rapid initially. This reaction slows down and stops before all of the calcium has reacted.

Use your knowledge of the solubilities of Group 2 sulfates to explain why these reactions of magnesium and calcium with dilute sulfuric acid are so different.

Page 24 of 71 ______

______

______(3) (Total 10 marks)

Q23. Barium chloride solution was added, dropwise, to magnesium sulfate solution until no more white precipitate was formed. The mixture was filtered.

Give the formulae of the two main ions in the filtrate.

______

______(Total 1 mark)

Q24. (a) Figure 1 shows the volume of hydrogen gas collected when a sample of magnesium reacted with an excess of dilute hydrochloric acid.

The rate of this reaction can be studied by measuring the time it takes for a given volume of hydrogen to be collected.

Figure 1

Page 25 of 71 Time / s

(i) State the meaning of the term rate of reaction.

______

______(1)

(ii) State and explain what has happened to the rate of this reaction at point W in Figure 1.

______

______(2)

(iii) In terms of collision theory explain why, at a fixed temperature, the rate of this reaction doubles when the concentration of the hydrochloric acid doubles.

______

______(2)

(b) In a study of the reaction in part (a), a student referred to activation energy.

(i) State the meaning of the term activation energy.

______

______(1)

(ii) Complete Figure 2 by drawing the shape of the reaction profile from reactants to products for an exothermic reaction. Show the position of the products. Show and label the activation energy.

Figure 2

Page 26 of 71

(2)

(i) Write an equation for the reaction of barium with water.

______(1)

(ii) A solution containing barium ions can be used to show the presence of sulfate ions in an aqueous solution of sodium sulfate.

Write the simplest ionic equation for the reaction that occurs and state what is observed.

Simplest ionic equation

______

Observation

______(2)

(iii) State one use of barium sulfate in medicine. Explain why this use is possible, given that solutions containing barium ions are poisonous.

Use ______

______

Explanation ______

______

______(2)

Page 27 of 71 (Total 13 marks)

Q25. There are many uses for compounds of barium.

(a) (i) Write an equation for the reaction of barium with water.

______(1)

(ii) State the trend in reactivity with water of the Group 2 metals from Mg to Ba

______(1)

(b) Give the formula of the least soluble hydroxide of the Group 2 metals from Mg to Ba

______(1)

(c) State how barium sulfate is used in medicine. Explain why this use is possible, given that solutions containing barium ions are poisonous.

Use ______

______

Explanation ______

______

(Extra space) ______

______(2) (Total 5 marks)

Q26. Group 2 elements and their compounds have a wide range of uses.

(a) For parts (a)(i) to (a)(iii), draw a ring around the correct answer to complete each sentence.

decreases.

(i) From Mg(OH)2 to Ba(OH)2, the solubility in water increases.

stays the same.

(1)

Page 28 of 71 decreases.

(ii) From Mg to Ba, the first ionisation energy increases.

stays the same.

(1)

decreases.

(iii) From Mg to Ba, the atomic radius increases.

stays the same.

(1)

(b) Explain why calcium has a higher melting point than strontium.

______

(Extra space) ______

______(2)

(i) State why sulfuric acid should not be used to acidify the barium chloride.

______

______(1)

(ii) Write the simplest ionic equation for the reaction that occurs when acidified barium chloride solution is added to a solution containing sulfate ions.

______(1) (Total 7 marks)

Q27. (a) Some scientists thought that the waste water from a waste disposal factory contained two sodium halides.

Page 29 of 71 They tested a sample of the waste water.

They added three reagents, one after the other, to the same test tube containing the waste water.

The table below shows their results.

Reagent added Observations 1. Silver nitrate solution (acidified A cream precipitate formed with dilute nitric acid)

2. Dilute ammonia solution A yellow precipitate remained

3. Concentrated ammonia solution The yellow precipitate did not dissolve

(i) Identify the yellow precipitate that did not dissolve in concentrated ammonia solution. Write the simplest ionic equation for the formation of this precipitate from silver ions and the correct halide ion. Identify the other sodium halide that must be present in this mixture of two sodium halides.

______

______(3)

(ii) Give one reason why the silver nitrate solution was acidified before it was used in this test.

______

______(1)

(iii) The method that the scientists used could not detect one type of halide ion. Identify this halide ion. Give one reason for your answer.

______

______(2)

Page 30 of 71 (b) The scientists thought that the waste water also contained dissolved barium ions. An aqueous solution of sodium sulfate can be used to test for the presence of dissolved barium ions.

Write the simplest ionic equation for the reaction between barium ions and sulfate ions to form barium sulfate.

State what is observed in this reaction.

Give a use for barium sulfate in medicine and explain why this use is possible, given that solutions containing barium ions are poisonous.

______

______(4)

(c) The scientists also analysed the exhaust gases from an incinerator used to destroy waste poly(ethene). Mass spectrometry showed that there was a trace gas with a precise Mr = 28.03176 in the exhaust gases from the incinerator.

The table below contains some precise relative atomic mass data.

Atom Precise relative atomic mass

12C 12.00000

1H 1.00794

16O 15.99491

Use the data to show that the trace gas is ethene. Show your working.

Suggest why both ethene and carbon monoxide might have been identified as the trace gas if the scientists had used relative atomic masses to a precision of only one decimal place.

Write an equation for the incomplete combustion of ethene to form carbon monoxide and water only.

Ethene is used to make poly(ethene). Draw the displayed formula for the repeating unit of poly(ethene). Name this type of polymer.

Page 31 of 71 ______

______

______(5) (Total 15 marks)

Q28. Copper(II) sulfate solution, together with copper(II) carbonate (CuCO3) powder, can be used to determine the identity of three solutions A, B and C. The three solutions are known to be hydrochloric acid, barium chloride, and sodium chloride.

In Experiment 1 a small amount of copper(II) carbonate powder was added to each of the three solutions.

In Experiment 2 a dropping pipette was used to add 2 cm3 of copper(II) sulfate solution to each of the three solutions.

The results of these experiments are shown in the table below.

Experiment 1 Experiment 2 Addition of copper(II) Addition of copper(II) carbonate powder sulfate solution

Solution A no visible change white precipitate

Solution B no visible change no visible change

effervescence Solution C no visible change (bubbles of gas)

(a) Use the observations in the table to deduce which of the solutions, A, B or C is

hydrochloric acid ______

barium chloride ______(2)

Page 32 of 71 (b) Explain why a precipitate was formed when copper(II) sulfate solution was added to solution A. Write an equation for the reaction that occurred.

Explanation ______

______

Equation ______(2)

______(1)

(d) Identify the two reagents that could be used in a test to confirm that the solutions contained chloride ions, not bromide ions. State what would be observed on addition of each reagent.

Reagent 1 ______

Observation 1 ______

______

Reagent 2 ______

Observation 2 ______

______(4)

(e) Copper(II) sulfate is toxic. Suggest one safety precaution you would take to minimise this hazard when wiping up a spillage of copper(II) sulfate solution.

______(1) (Total 10 marks)

Q29. Desalination is a technique for making drinking water by the removal of salts from sea water. It is used in parts of the world where fresh water is in short supply. A problem with this technique is the increase in the concentration of salts, particularly of sodium chloride, in the effluent (the solution returned to the sea).

Desalination uses a process called reverse osmosis. In this process, sea water under high pressure is passed over a special membrane which allows only pure water to pass through it.

The owners of a desalination plant have asked for the effluent to be analysed at different operating pressures. This is needed to find an approximate value for the maximum operating pressure that gives an effluent that has a minimum harmful effect on the environment.

Page 33 of 71 A chemist sampled the effluent at different pressures. For each pressure, a 250 cm3 sample of effluent was taken in a measuring cylinder and poured into a weighed beaker. The water was evaporated by heating and the beaker reweighed. The following results were obtained.

Experiment 1 2 3 4 5 6

Pressure / MPa 0.1 0.5 1.0 2.5 4.0 8.0

Beaker mass before 55.3 55.5 55.0 55.1 55.3 56.3 heating / g

Beaker mass after 62.5 64.9 65.3 66.6 67.5 69.4 heating / g

Mass of solid in

beaker / g

(a) Complete the table above to determine the mass of solid that remains in the beaker at each pressure.

Plot a graph of mass of solid (y-axis) against pressure on the graph paper.

Draw a smooth curve through the points.

Page 34 of 71

(4)

(b) To minimise harmful effects on the environment, the concentration of sodium chloride in the effluent should not exceed 44.0 g dm–3. Use your graph to find a value for the pressure, in MPa, that the chemist should advise to be the maximum operating pressure.

Assume that all the solid left in the beaker is sodium chloride.

______

Page 35 of 71 (1)

(c) In Experiment 1 the 250 cm3 sample of the effluent contained the same amount of sodium chloride as the original sea water. Calculate the concentration, in mol dm–3, of sodium chloride in sea water.

Assume that all the solid left in the beaker is sodium chloride. Show your working.

______

______(2)

(d) For the measuring cylinder and the balance, the maximum total errors are shown below. These errors take into account multiple measurements.

250 cm3 measuring cylinder ±1.0 cm3 balance ±0.1 g

Estimate the maximum percentage error in using these pieces of apparatus, and hence estimate their combined error.

You should use the mass of the solid in the beaker in Experiment 1 to estimate the percentage error in using the balance. Show your working.

______

______(2)

(e) Consider your graph.

(i) Is the curve good enough to use with confidence to predict the intermediate values? Explain your answer.

______

______(1)

(ii) Identify the anomalous results, if any.

______

______(1)

Page 36 of 71 (f) Give one reason why the owners of the plant were satisfied with the maximum operating pressure determined in part (b) despite the combined errors you have calculated in part (d).

______

______(1)

(g) (i) Suggest one harmful effect that effluent with a high concentration of sodium chloride might have if it is returned to the sea.

______

______(1)

(ii) Suggest one low cost method of treating the effluent so that this harmful effect could be reduced.

______

______(1)

(h) Bromine can be obtained by reacting the bromide ions in the concentrated sea water using chlorine gas in a displacement reaction. Write an equation for this reaction.

______

______(1)

(i) The solid obtained by the chemist after heating the effluent to dryness was treated with concentrated sulfuric acid. A vigorous reaction resulted, including the formation of a purple vapour of iodine. Give one reason why this procedure could not be adapted to be an economic method for producing iodine from sea water on an industrial scale.

______

______(1)

(j) Sea water contains some organic material. After removing all the water, by heating the effluent samples strongly, it was noticed that the solid formed contained black particles. These particles are insoluble in water.

On heating very strongly in air these particles burned to give a colourless gas.

(i) Identify these black particles.

______

Page 37 of 71 (1)

(ii) Suggest how these black particles are formed by heating the effluent strongly.

______

______(1)

(iii) Suggest how a sample of the black particles could be separated from the solid formed.

______

______(2)

(k) The water produced by some desalination plants is acidic due to the presence of hydrochloric acid. Lime, Ca(OH)2, is added to neutralise this acid. Write an equation for this reaction.

______(1)

(l) Lime is used because it is relatively inexpensive and available in large quantities. Identify one other large-scale use of lime.

______(1) (Total 22 marks)

Q30. Group 2 metals and their compounds are used commercially in a variety of processes and applications.

(a) State a use of magnesium hydroxide in medicine.

______(1)

(b) Calcium carbonate is an insoluble solid that can be used in a reaction to lower the acidity of the water in a lake.

Explain why the rate of this reaction decreases when the temperature of the water in the lake falls.

______

Page 38 of 71 ______(3)

(i) Explain why strontium has a higher melting point than barium.

______

______(2)

(ii) Write an equation for the reaction of strontium with water.

______(1)

(d) Magnesium can be used in the extraction of titanium.

(i) Write an equation for the reaction of magnesium with titanium(IV) chloride.

______(1)

(ii) The excess of magnesium used in this extraction can be removed by reacting it with dilute sulfuric acid to form magnesium sulfate.

Use your knowledge of Group 2 sulfates to explain why the magnesium sulfate formed is easy to separate from the titanium.

______

______(1) (Total 9 marks)

Q31. Pure hydrogen peroxide is a colourless liquid with a boiling point of 150 °C. Hydrogen peroxide was originally produced commercially in a two-stage process. In the first stage barium was heated in air to form barium peroxide. In the second stage barium peroxide was added to aqueous nitric acid. The equations for the reactions are shown below.

Stage 1 Ba(s) + O2(g) BaO2(s)

Stage 2 BaO2(s) + 2HNO3(aq) H2O2(aq) + Ba(NO 3)2(aq)12

Page 39 of 71 (a) Suggest one method of separating hydrogen peroxide from the reaction mixture in Stage 2.

______

______(1)

(b) Apart from cost, suggest one reason why nitric acid was eventually replaced by sulfuric acid in Stage 2.

______

______(1)

(c) Suggest one reason why infrared spectroscopy could not be used to indicate the presence of a small amount of water in hydrogen peroxide.

______

______(1) (Total 3 marks)

Q32. Both strontium carbonate and strontium sulfate are white solids which are insoluble in water. Strontium carbonate reacts with hydrochloric acid to produce a solution of strontium chloride. Strontium sulfate does not react with hydrochloric acid.

Describe how you would obtain strontium sulfate from a mixture of strontium carbonate and strontium sulfate.

______

______(Total 2 marks)

Q33. The elements in Group 2 can be used to show the trends in properties down a group in the Periodic Table.

(a) State the trend in atomic radius down Group 2 from Mg to Ba and give a reason for this trend.

Trend ______

Reason ______(2)

Page 40 of 71 (b) State and explain the trend in melting points of the elements down Group 2 from Mg to Ba.

Trend ______

Explanation ______

______

______(3)

(c) State the trend in reactivity with water of the elements down Group 2 from Mg to Ba. Write an equation for the reaction of magnesium with steam and an equation for the reaction of strontium with water.

Trend ______

Equation for magnesium ______

Equation for strontium ______(3)

(d) Sulfates of the Group 2 elements from Mg to Ba have different solubilities. Give the formula of the least soluble of these sulfates and state one use that depends upon the insolubility of this sulfate.

Formula ______

Use ______(2) (Total 10 marks)

Q34. Which one of the following is a correct procedure for isolating a sample of hydrated copper(II) sulphate from a mixture of hydrated copper(II) sulphate and barium sulphate?

A filter, crystallise filtrate, dry the crystals

B filter, dry the solid on the filter paper

C add water, filter, dry the solid left on the filter paper

D add water, filter, crystallise filtrate, dry the crystals (Total 1 mark)

Q35. State the trends in solubility of the hydroxides and of the sulphates of the Group II elements Mg–Ba.

Describe a chemical test you could perform to distinguish between separate aqueous solutions of sodium sulphate and sodium nitrate. State the observation you would make with each solution. Write an equation for any reaction which occurs.

Page 41 of 71 (Total 6 marks)

Page 42 of 71 Mark schemes

Q1. (a) Ba2+ OR Sr2+ 1 Award M1 if barium named in M1 then used Ba2+ in the equation 2− 2+ M2 SO4 (aq) + Ba (aq) BaSO4 (s) 1 ⟶ (b) OH− Award M1 if hydroxide named in M1 then used OH− in the equation 1 2+ − Mg (aq) + 2OH (aq) Mg(OH)2 (s) 1 ⟶ [4]

Q2. (a) BaCl2 / Ba(OH)2 / Ba(NO3)2 / BaX2 or names

Ignore acidification but CE = 0/3 if H2SO4 If reagent incorrect or blank then CE =0/3 If Ba2+ or wrong formula, lose M1 and mark on 1

colourless solution / no (visible) change (nvc) / no ppt / no (visible) reaction Ignore nothing happens and no observation 1

white precipitate / white solid 1

(b) NaOH / sodium hydroxide / other Group 1 hydroxides If reagent incorrect or blank then CE =0/3 If reagent incomplete, lose M1 and mark on 1

white precipitate / white solid 1

(white) ppt which dissolves in excess (NaOH) If reagent is excess NaOH, allow colourless solution for M3 1

Alternative Method

Name or formula of Group 1 carbonate 1

white precipitate / white solid 1

(white) precipitate and effervescence 1

Page 43 of 71 [6]

Q3. (a) CO2 gas escapes or is lost 1

(b) Mass CO2 = 16.11 − 14.58 = 1.53 g 1

Mr CO2 = 44.0

−2 Mol CO2 = 1.53 / 44.0 = 3.48 × 10 1

−2 Mol SrCO3 = 3.48 × 10 1

−2 Mass SrCO3 = mol × Mr = 3.48 × 10 × 147.6

Mass SrCO3 = 5.13 (g) 1 mark for the answer and 1 for 3 sf precision Allow 5.14 g (as a result of rounding) 2

= 0.160 (%) 1

(d) Original Mass SrO = 6.26 − 0.347 − 5.13

= 0.783 g (or 783 mg) OR 6.26 − 0.347 − 4.85 = 1.063 g Allow 0.773 g or 773 mg (from rounding error in part (b) 1

Justification: All SrCO3 reacted because heated to constant mass. 1

(e) 3SrO + 2Al Al2O3 + 3Sr 1 ⟶ Al acts as a reducing agent 1

Sr is collected as a vapour because 1

Al2O3 is an ionic lattice and so has strong ionic attractions 1

Than Sr which is a metallic structure with (relatively) weaker bonding 1 [14]

Q4.

Page 44 of 71 (a) Ca + 2H2O Ca(OH)2 + H2 1 ⟶ 8 − 12 1

(b) Decrease 1

Allow Ba(NO3)2 or other soluble barium salt 1

2+ 2− Ba + SO4 BaSO4 Allow equation if state symbols missing but penalise if state symbols⟶ are incorrect 1

(d) Strong attraction 1

Between positive and negative ions 1 [7]

Q5. (a) 1s22s22p63s23p64s2 Allow correct numbers that are not superscripted 1

2+ – (b) Ca(s)+ 2H2O(l) Ca (aq) + 2OH (aq) + H2(g) State symbols essential 1

(d) Ca(g) Ca+(g) + e– State symbols essential Allow ‘e’ without the negative sign 1

(e) Decrease If answer to ‘trend’ is not ‘decrease’, then chemical error = 0 / 3 1

Ions get bigger / more (energy) shells Allow atoms instead of ions 1

Weaker attraction of ion to lost electron 1 [7]

Page 45 of 71 Q6. (a) Q is calcium or magnesium 1

bromide 1

R is aluminium 1

chloride 1

S is iron(III) 1

sulfate 1 Mark this question independently

2+ 2– (b) Ba + SO4 BaSO4 1

3+ – [Fe(H2O)6] + 3OH Fe(H2O)3(OH)3 + 3H2O 1

3+ 2– 2[Fe(H2O)6] + 3CO3 2Fe(H2O)3(OH)3 + 3H2O + 3CO2 1

3+ – – [Fe(H2O)6] + 4Cl [FeCl4] + 6H2O 1 [10]

Q7. (a) Sulfuric acid has 2 × the H+ ion concentration Larger concentration of H+ is sufficient. 1

Calcium is more reactive (than magnesium) Allow reference to a greater surface area for calcium. Do not allow any references to temperature variations. 1

(b) Calcium sulfate

Accept CaSO4 1

Ca + H2SO4 → CaSO4 + H2 2+ 2– Accept Ca + SO4 → CaSO4 Allow multiples or fractions of these equations. Ignore state symbols. 1

Calcium sulfate is insoluble or has (very) low solubility Accept “an insoluble layer is formed”.

Page 46 of 71 Answer must refer to the low solubility. 1 [5]

Q8. Identifies precipitate as being BaSO4 1 Moles of Barium sulfate = mass/Mr (= 0.764 / 233.4) = 0.003273 moles

Allow conseq if Mr BaSO4 or BaCl2 incorrect 1 Mass of Barium chloride = 208.3 × 0.003273 = 0.6818 g 1

Percentage of Magnesium chloride Do NOT penalise incorrect precision here Allow range 33.7-35.5% (rounding errors penalised elsewhere in paper) 1 [4]

Q9. A [1]

Q10. A [1]

Q11. (a) More (electron) shells / (outer) electrons further from the nucleus / larger atoms / more shielding If ‘molecules’ mentioned CE = 0 It = Ba Mark independently ALLOW energy levels for shells Both ideas must be comparative 1 So weaker attraction of nucleus/protons for (outer) electrons NOT hold/pull/bonded for ‘attraction’ Idea of nucleus or protons must be clear ALLOW M2 if electrons implied from mention in M1 ALLOW converse if it is clear that answer refers to Ca 1

(b) White solid / white ash ALLOW ‘white smoke/powder’ IGNORE ‘product’

Page 47 of 71 NOT ppt IGNORE fumes IGNORE tube/glass goes black 1

Bright light / white light ALLOW glow/flame for light 1

Mg + H2O → MgO + H2 IGNORE state symbols 1

(c) BaSO4 is insoluble but Ba(NO3)2 is soluble OR BaSO4 precipitates but Ba(NO3)2 product(s) of second reaction is soluble/remains in solution OR BaSO4 is insoluble but no reaction occurs in second case NOT just ‘no observation’ in second case Comparison of solubilities must be implied NOT Barium is soluble/insoluble Correct state symbols required 1

2+ 2- Ba (aq) + SO4 (aq) → BaSO4(s) 1 [7]

Q12. (a) M1 acidified potassium dichromate or K2Cr2O7 / H2SO4

+ OR K2Cr2O7 / H OR acidified K2Cr2O7

M2 (orange to) green solution OR goes green

M3 (solution) remains orange or no reaction or no (observed) change If no reagent or incorrect reagent in M1, CE = 0 and no marks for M1, M2 or M3 If incomplete / inaccurate attempt at reagent e.g. “dichromate” or “dichromate(IV)” or incorrect formula or no acid, penalise M1 only and mark on For M2 ignore dichromate described as “yellow” or “red” For M3 ignore “nothing (happens)” or “no observation”

Alternative using KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate or KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 colourless solution OR goes colourless

M3 (solution) remains purple or no reaction or no (observed) change

Page 48 of 71 For M1 If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark on

Credit alkaline KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green 3

(b) M1 (Shake with) Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)

M2 (stays) orange / red / yellow / brown / the same

OR no reaction OR no (observed) change

M3 decolourised / goes colourless / loses its colour / orange to colourless If no reagent or incorrect reagent in M1, CE = 0 and no marks for M1, M2 or M3 If incomplete / inaccurate attempt at reagent (e.g. Br), penalise M1 only and mark on No credit for combustion observations; CE = 0 For M2 in every case Ignore “nothing (happens)” Ignore “no observation” Ignore “clear”

OR as alternatives

Use KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate OR KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 (stays) purple or no reaction or no (observed) change

M3 decolourised / goes colourless / loses its colour

Use iodine

M1 iodine or I2 / KI or iodine solution

M2 no change

M3 decolourised / goes colourless / loses its colour

Use concentrated sulfuric acid

M1 concentrated H2SO4

M2 no change

M3 brown For M1, it must be a whole reagent and / or correct formula For M1 penalise incorrect attempt at correct formula, but

Page 49 of 71 mark M2 and M3 With potassium manganate(VII) If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark on

Credit alkaline / neutral KMnO4 for possible full marks but M3 gives brown precipitate or solution goes green Apply similar guidance for errors in the formula of iodine or concentrated sulfuric acid reagent as those used for other reagents. 3

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble iodide including HI

M2 yellow precipitate or yellow solid / yellow suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble bromide including HBr

M2 cream precipitate or cream solid / cream suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 NaOH or KOH or any soluble carbonate

M2 brown precipitate or brown solid / brown suspension with NaOH / KOH (white precipitate / solid / suspension with carbonate)

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear If no reagent or incorrect reagent or insoluble chloride in M1, CE = 0 and no marks for M1, M2 or M3 Allow chlorine water If incomplete reagent (e.g. chloride ions) or inaccurate attempt at formula of chosen chloride, or chlorine, penalise M1 only and mark on For M2 require the word “white” and some reference to a solid. Ignore “cloudy solution” OR “suspension” (similarly for the alternatives) For M3

Page 50 of 71 Ignore “nothing (happens)” Ignore “no observation” Ignore “clear” on its own Ignore “dissolves” 3

(d) M1 Any soluble sulfate including (dilute or aqueous) sulfuric acid

M2 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

M3 white precipitate or white solid / white suspension If no reagent or incorrect reagent or insoluble sulfate in M1, CE = 0 and no marks for M1, M2 or M3

Accept MgSO4 and CaSO4 but not barium, lead or silver sulfates If concentrated sulfuric acid or incomplete reagent (e.g. sulfate ions) or inaccurate attempt at formula of chosen sulfate, penalise M1 only and mark on For M3 (or M2 in the alternative) require the word “white” and some reference to a solid. Ignore “cloudy solution” OR “suspension” For M2 (or M3 in the alternative) Ignore “nothing (happens)” Ignore “no observation” Ignore “clear” on its own Ignore “dissolves”

OR as an alternative

M1 NaOH or KOH

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear If incomplete reagent (e.g. hydroxide ions) or inaccurate attempt at formula of chosen hydroxide, penalise M1 only and mark on

If M1 uses NH3 (dilute or concentrated) penalise M1 only and mark on 3 [12]

Q13. (a) M1 Increases / gets bigger If M1 is incorrect CE = 0 for the clip If M1 is blank, mark on and seek to credit the correct information in the text

M2 requires a correct M1 M2 requires correct M1

Page 51 of 71 More shells or sub-shells or (main) levels or sub-levels or orbitals (of electrons) If “molecules” penalise M2 Not simply “more electrons” Not “more outer shells” Ignore reference to nuclear charge and shielding 2

(b) (i) Increases / gets more reactive / reacts more vigorously / violently (down the Group) 1

(ii) Sr + 2H2O Sr(OH)2 + H2 Credit multiples and correct ionic equations Ignore state symbols 1

Q14. ZnCO3 → ZnO + CO2 Ignore state symbols. If equation incorrect, allow one mark only for correct atom economy method. 1

Percentage atom economy = Mark consequentially for incorrect formula mass(es) 1

× 100 = 64.9 Accept answer to at least 2 significant figures 1 [3]

Q15. (a) Compound 1 If M1 incorrect, CE = 0

M1 1

No visible change with H2SO4

M2 1

Page 52 of 71 Gives white ppt with NaOH

M3 1

(b) BaCO3 1

The carbonate ion releases CO2 1

but the BaSO4 formed is highly insoluble. 1

Sr(OH)2 + H2SO4 SrSO4 + 2H2O Allow ionic equation; ignore state symbols 1 [8]

Q16. (a) 0.155 g per 100 cm3

M1 Allow 0.153 − 0.157 1

(0.155 / 74.1) × 10 = 0.0209 mol dm−3

M2 Allow 0.0206 − 0.0212 1

Answer to 3 significant figures

M3 The correct answer only loses M1 1

(b) Take a known volume of the saturated solution 1

Evaporate the filtrate to dryness

Allow titrate with dilute HCl or HNO3 ..... 1

Weigh the residue .....of known / specified concentration Ignore any references to indicators 1 [6]

Q17. (a) M1 Used in a barium meal / barium swallow / barium enema

Page 53 of 71 OR (used to absorb) X-rays Credit a correct reference to M1 written in the explanation in M2 unless contradictory.

M2 BaSO4 / barium sulfate / it is insoluble For M2 penalise obvious reference to barium or to barium ions being insoluble. 2

(b) Mg(OH)2 + 2HCl MgCl2 + 2H2O Or multiples. Ignore state symbols. 1

(c) It / magnesium hydroxide is insoluble / insufficiently soluble / sparingly soluble / less soluble than barium hydroxide / forms low concentration solutions Weak alkali alone is insufficient. Formation of a precipitate needs explanation. 1

(d) TiCl4 + 2Mg 2MgCl2 + Ti Or multiples. Ignore state symbols. 1

(e) M1 Hydrogen / H2 produced

OR an equation to produce hydrogen / H2

( eg Mg + 2H2O Mg(OH)2 + H2)

( eg Mg + H2O MgO + H2) For M1

Do not penalise an incorrect equation; the mark is for H2 or hydrogen. Award one mark only for ‘exothermic reaction with steam / H2O’ for a student who has not scored M1

M2 requires correct M1

risk of explosion

OR forms explosive mixture (with air)

OR (highly) flammable Ignore ‘violent’ reaction. 2 [7]

Q18. (a) (i) SrCl2(aq) + Na2SO4(aq) → SrSO4(s) + 2NaCl(aq) Allow multiples, including fractions. Allow ionic equations. Lose this mark if any of the state symbols are missing or

Page 54 of 71 incorrect. 1

(ii) Add nitric acid to the mixture (until in excess) Do not allow any suggestion that the solution is an emetic. 1

Filter (to isolate strontium sulfate) 1

(b) Insoluble barium sulfate is formed Allow ‘removes barium ions as a precipitate’. 1

(c) Add silver nitrate, then dilute ammonia (solution) M1 Do not allow answers which imply silver nitrate and ammonia are added at the same time. Allow ‘add silver nitrate, then concentrated ammonia (solution)’. Can score M1 in the answer for M3 1

Cream precipitate M2 Allow ‘off white precipitate’. 1

No visible change or precipitate dissolves slightly in dilute ammonia M3 Allow ‘soluble / colourless solution / precipitate dissolves in concentrated ammonia’. Allow 3 marks for: Add dilute ammonia (solution), then silver nitrate M1 No visible change M2 Cream / off white precipitate with silver nitrate M3 1 [7]

Q19. (a) (i) 1.08 × 10–2 Do not penalise precision but must be to at least 2 significant figures. Do not accept 1 × 10–2 1

(ii) 5.4(0) × 10–3 Allow (i) / 2 Do not penalise precision but must be to at least 2 significant figures. 1

(iii) 266.6 Lose this mark if answer not given to 1 decimal place. 1

(iv) mass = 5.4(0) × 10–3 × 266.6 = 1.44 g M1

Page 55 of 71 Allow (ii) × (iii). 1

percentage = 1.44 × 100 / 2.25 = 64.0 M2 Allow consequential answer from M1 Lose this mark if answer not given to 3 significant figures. Correct answer with no working scores M2 only. 1

(v) 1 Would give an incorrect / too large mass (of silver chloride) Do not allow ‘to get an accurate result’ without qualification. 1

2 To remove soluble impurities / excess silver nitrate (solution) / strontium nitrate (solution) Do not allow ‘to remove impurities’. Do not allow ‘to remove excess strontium chloride solution’. 1

2+ - (b) (i) Mg (aq) + 2OH (aq) → Mg(OH)2(s) 2+ - 2+ - Allow Mg (aq) + 2OH (aq) → Mg (OH )2(s) Allow multiples, including fractions. Lose mark if state symbols are missing or incorrect. Lose mark if incorrect charge on an ion. 1

(ii) Does not produce CO2 / gas which distends stomach / does not produce wind / does not increase pressure in stomach Allow ‘prevents flatulence’ and ‘prevents burping’. Do not allow ‘gas’ without qualification. 1

Allow propanone as C3H6O - 2+ 2+ 2- Allow (CH3COO )2Ca → CH3COCH3 + Ca CO3 1

(d) Ca (salt) - no visible change with sodium chromate(VI) M1 Allow ‘yellow solution formed’ or ‘no ppt. forms’. Allow M1 and M2 in any order. 1

Sr and Ba (salts) give (yellow) precipitate with sodium chromate(VI) M2 Lose this mark if precipitate has an incorrect colour. 1

Sr precipitate (chromate(VI)) dissolves in ethanoic acid / Ba precipitate (chromate(VI)) does not dissolve in ethanoic acid M3 If ethanoic acid is added first, allow access to M1 and M3. 1

(e) C 42.09 / 12, H 2.92 / 1, N 8.18 / 14, O 37.42 / 16 and S 9.39 / 32.1 Accept any other correct method of working.

Page 56 of 71 If relative atomic mass has been divided by the percentage composition is used then CE = 0 / 2 1

C12H10N2O8S Correct answer with no working scores 1 mark only. 1 [15]

Q20. (a) (Measure the) volume of gas / mass of the container + contents 1

Suitable named piece of equipment Gas syringe (or inverted burette or measuring cylinder, as long as student has referred to the cylinder being filled with water) / balance. Equipment must be correct for the measurement stated. 1

(b) Any one of:

• Mass of magnesium Allow amount of magnesium.

• Surface area of magnesium 1

Vacuum: Sealed container with a side arm and Buchner or Hirsch funnel Must be either gravity filtration (with a V-shaped funnel) or vacuum filtration (with a side-arm conical flask) appropriately drawn. 1

Filter paper Must show filter paper as at least two sides of a triangle (V- shaped) for gravity filtration or horizontal filter paper for vacuum filtration. 1

(ii) Wash with / add (a small amount of cold) water Ignore filtering. 1 [6]

Q21. (a) M1 (could be scored by a correct mathematical expression Correct answer to the calculation gains all of M1, M2 and M3

M1 ΔH = ΣΔHf (products) − ΣΔH f (reactants) Credit 1 mark for − 101 (kJ mol−1)

Page 57 of 71 OR a correct cycle of balanced equations

M2 = − 1669 − 3(− 590) = − 1669 + 1770 (This also scores M1)

M3 = + 101 (kJ mol−1)

Award 1 mark ONLY for − 101 For other incorrect or incomplete answers, proceed as follows • check for an arithmetic error (AE), which is either a transposition error or an incorrect multiplication; this would score 2 marks (M1 and M2) • If no AE, check for a correct method; this requires either a correct cycle with 3Sr and 2Al OR a clear statement of M1 which could be in words and scores only M1

M4 - Using powders Any one from

• To increase collision frequency / collisions in a given time / rate of collisions

• To increase the surface contact / contact between the solids / contact between (exposed) particles Ignore dividing final answer by 3 Penalise M4 for reference to molecules. 5

M5 Major reason for expense of extraction Any one from

• Aluminium is extracted by electrolysis OR aluminium extraction uses (large amounts of) electricity

• Reaction / process / It / the mixture requires heat

• It is endothermic

(b) Calcium has a higher melting point than strontium, because Ignore general Group 2 statements.

Correct reference to size of cations / proximity of electrons M1 (For Ca) delocalised electrons closer to cations / positive ions / atoms / nucleus OR cations / positive ions / atoms are smaller OR cation / positive ion / atom or it has fewer (electron) shells / levels Penalise M1 if either of Ca or Sr is said to have more or less delocalised electrons OR the same nuclear charge. Ignore reference to shielding.

Relative strength of metallic bonding M2 (Ca) has stronger attraction between the cations / positive ions / atoms / nucleus and the delocalised electrons OR

Page 58 of 71 stronger metallic bonding

(assume argument refers to Ca but credit converse argument for Sr) CE= 0 for reference to molecules or Van der Waals forces or intermolecular forces or covalent bonds. 2

M2 Mg + 2H2O Mg(OH)2 + H2 Credit multiples of the equations.

M3 Magnesium hydroxide is used as an antacid / relieve indigestion (heartburn) / neutralise (stomach) acidity / laxative Not simply “milk of magnesia” in M3 3 [10]

Q22. (a) As concentration increases the amount of heat given out increases / temperature increases (M1) Any order. Ignore references to an exothermic reaction. 1

More successful collisions or reactions in a given time OR more particles have the activation energy (M2) Allow could be a second / nth order reaction. 1

(An increase in temperature or more heat given out) increases the rate of a reaction (M3) 1

(b) The magnesium is coated with an oxide / MgO (M1) Allow magnesium hydroxide. 1

MgO / the coating / the corrosion product has to be removed before Mg will react OR Mg and MgO / the coating / the corrosion product react at different rates OR Initially MgO / the coating / the corrosion product reacts not Mg (M2) Ignore inert coating. 1

Slower with hot water or faster with steam

The hot water produces Mg(OH)2 / the hydroxide OR steam produces MgO / the oxide

(Slow) bubbling with hot water OR bright white light / flame / white solid with steam 2 max

Page 59 of 71 (d) Magnesium sulfate is soluble and calcium sulfate is insoluble / slightly soluble / magnesium sulfate is more soluble / calcium sulfate is less soluble / correct trend in solubility (M1) Any order. M1 requires a comparison of the two solubilities.

Calcium sulfate coats the surface of the calcium (M2)

Coating prevents further contact with / reaction by the acid (M3) ‘Calcium sulfate forms a protective coating’ scores M2 only. 3 [10]

Q23. Mg2+ and Cl– Do not allow names. [1]

Q24. (a) (i) Change in concentration (of a substance / reactant / product) in unit time / given time / per (specified) unit of time This may be written mathematically OR may refer to the gradient of a graph of concentration / volume against time

Amount of substance formed / used up in unit time / given time / per (specified) unit of time Ignore additional information including reference to collisions 1

(ii) At W

M1 (QoL)

The rate / it is zero

The magnesium has all reacted / has been used up Ignore reference to the acid being used up

No more collisions possible between acid and Mg

Reaction is complete / it has stopped

No more hydrogen / product is produced 2

Page 60 of 71 (iii) M1

Twice / double as many particles / hydrogen ions (in a given volume) Penalise reference to (hydrochloric acid) molecules in M1 Penalise reference to “HCl particles” in M1

Twice / double as much hydrochloric acid

Twice / double as many effective / successful collisions (in a given time)

Twice / double as many collisions with either sufficient energy to react OR with E ≥ Ea

double the successful / effective collision frequency 2

(b) (i) The activation energy is the minimum energy for a reaction to go / start

Minimum energy for a successful/ effective collision 1

(ii) M1 Products lower than reactants on the profile Mark independently

M2 Activation energy (Ea) shown and labelled correctly from reactants to peak of curve Mark independently 2

Ba + 2H2O Ba2+ + 2OH− + H2 Allow multiples Ignore state symbols 1

(ii) M1 Ba2+ + SO42− BaSO4 Ignore state symbols in M1 Not multiples in M1

M2 White precipitate / solid Extra ions must be cancelled Penalise contradictory observations in M2 2

(iii) M1 Barium meal / barium swallow / barium enema

Page 61 of 71 Accept a correct reference to M1 written in the explanation in M2, unless contradictory

OR used in X-rays OR to block X-rays OR X-ray contrast medium OR CT scans

M2 BaSO4 / barium sulfate is insoluble (and therefore not toxic) For M2 NOT barium ions NOT barium NOT barium meal and NOT “It” Ignore radio-tracing 2 [13]

Q25. (a) (i) Ba + 2H2O Ba(OH)2 + H2 Ignore state symbols Credit multiples and correct ionic equations 1

(ii) (Reactivity with water) increase(s) / increasing / increased (down the Group / from Mg to Ba) Accept “greater” or “gets more” or similar words to that effect. Ignore reference to “increase in solubility / gets more soluble” 1

(b) Mg(OH)2 2+ – Accept Mg (OH )2 / Mg(HO)2 Insist on brackets and correct case 1

M2 BaSO4 / barium sulfate is insoluble (and therefore not toxic) Accept a correct reference to M1 written in the explanation in M2, unless contradictory For M2 NOT barium ions NOT barium NOT barium meal and NOT “It” Ignore radio-tracing 2 [5]

Q26. (a) (i) Increases 1

(ii) Decreases 1

Page 62 of 71 (iii) Increases 1

(b) Calcium has a higher melting point than strontium, because CE = 0 for reference to molecules or intermolecular forces or covalent bonds

Correct reference to size of cations/proximity of electrons

M1 (For Ca) delocalised electron(s) closer to cations / positive ions / nucleus Ignore “Van der Waals forces (between atoms)” but penalise if between “molecules”

OR cations / positive ions / atoms are smaller

OR cation / positive ion / atom or it has fewer (electron) shells / levels Ignore general Group 2 statements Answers must be specific

Relative strength of metallic bonding

M2 (For Ca) has stronger attraction between the cations / positive ions / nucleus and the delocalised electron(s) Penalise M1 if Ca or Sr is said to have more or less delocalised electrons

stronger metallic bonding

(assume argument refers to Ca but accept converse argument for Sr) Ignore reference to shielding 2

2– (c) (i) Sulfuric acid / it contains sulfate ions / SO4

OR Do not penalise an additional but incorrect formula for sulfate ion.

Sulfuric acid would form a (white) precipitate If only the formula of the sulfate ion is given, it must be correct 1

2+ 2– (ii) Ba + SO4 BaSO4 ONLY Ignore state symbols No multiples 1 [7]

Q27. (a) (i) M1 (yellow precipitate is) silver iodide OR AgI (which may be awarded from the equation)

Page 63 of 71 M2 Ag+ + I– → AgI (Also scores M1 unless contradicted)

M3 sodium chloride OR NaCl For M2 Accept multiples Ignore state symbols Allow crossed out nitrate ions, but penalise if not crossed out 3

(ii) The silver nitrate is acidified to

• react with / remove ions that would interfere with the test

• prevent the formation of other silver precipitates / insoluble silver compounds that would interfere with the test

• remove (other) ions that react with the silver nitrate

• react with / remove carbonate / hydroxide / sulfite (ions) Ignore reference to “false positive” 1

(iii) M1 and M2 in either order

M1 Fluoride (ion) OR F–

M2 • Silver fluoride / AgF is soluble / dissolves (in water)

• no precipitate would form / no visible /observable change Do not penalise the spelling “fluoride”, Penalise “fluride” once only Mark M1 and M2 independently 2

2+ 2- (b) M1 Ba + SO4 → BaSO4

(or the ions together)

M2 white precipitate / white solid / white suspension

M3 Barium meal or ( internal ) X-ray or to block X-rays

M4 BaSO4 / barium sulfate is insoluble (and therefore not toxic) For M1, ignore state symbols Allow crossed out sodium ions, but penalise if not crossed out For M2, ignore “milky”

If BaSO3 OR BaS used in M1 and M4, penalise once only For M3 Ignore radio-tracing For M4 NOT barium ions NOT barium NOT barium meal

NOT “It” unless clearly BaSO4

Page 64 of 71 4

M2 Ethene and CO or “they” have an imprecise Mr of 28.0 / 28

Ethene and CO or “they” have the same Mr to one d.p.

These may be shown by two clear, simple sums identifying both compounds

M3 C2H4 + 2O2 → 2CO + 2H2O

(H2C=CH2)

M4 Displayed formula

M5 Type of polymer = Addition (polymer) M1 must show working using 5 d.p.for hydrogen Penalise “similar” or “close to”, if this refers to the imprecise value in M2, since this does not mean “the same”

For M3, accept CH2=CH2 OR CH2CH2 For M4, all bonds must be drawn out including those on either side of the unit. Penalise “sticks” Ignore brackets around correct repeating unit but penalise “n” Penalise “additional” 5 [15]

Q28. (a) Hydrochloric acid = C 1

Barium chloride = A 1

(b) Barium sulfate is insoluble 1

CuSO4 + BaCl2 → BaSO4 + CuCl2 Accept multiples. Accept ionic equation.

Page 65 of 71 Do not penalise lack of state symbols, but if used they must be correct. 1

(d) Reagent 1 silver nitrate (solution) Ignore lack of reference to acidifying prior to addition of silver nitrate solution. 1

Observation 1 White precipitate 1

Reagent 2 (dilute) ammonia solution / aqueous ammonia Do not accept addition of ammonia only. 1

Observation 2 (Colourless) solution Allow ppt dissolves. Do not allow ‘goes colourless’ or ‘goes clear’. Chlorine and no visible change or solution does not become orange scores M3 and M4. 1

(e) Gloves / wash hands after use Ignore ‘eye protection’. Do not accept ‘do not ingest the chemicals’, ‘wipe up spillages’, ‘use a fume cupboard’, ‘wear a lab coat’ (list principle). 1 [10]

Q29. (a) Correct completion of table (7.2 – 9.4 – 10.3 – 11.5 – 12.2 – 13.1) Any error loses the mark. 1

Appropriate scales for axes No penalty for missing labels but the graph must cover at least half of the available area. 1

All points plotted correctly Allow ±1 small square. 1

Line of best fit acceptable Must be a reasonably smooth curve but make allowance for freehand drawing passing within one small square of each point. Do not penalise minor doubling of line. 1

Page 66 of 71 (b) Maximum mass at (44.0 / 4) = 11.0 g giving a max. pressure of 1.7 ± 0.1 MPa Allow this pressure range only. Check that candidate’s answer matches graph. 1

(c) 7.2 g of NaCl in 250 cm3 represents 28.8 g dm–3 Allow 0.49 but not 0.5; otherwise do not penalise precision of answer 1

Molarity = 0.492 mol dm–3 Conseq. to their graph value for 100 kPa to 2 or 3 sig. 1

(d) Measuring cylinder = (1 / 250) × 100 = 0.4% Balance = (0.1 / 7.2) × 100 = 1.4% Both values correct for the first mark. Balance error conseq. on their 100 kPa mass value. Ignore precision of answers. 1

Combined error 1.8% When error being calculated is not stated, allow if the calculations are in the same order as in the question (measuring cylinder, balance). If only combined error given then 1 mark only. 1

(e) (i) The points are good enough to be able to draw a smooth curve because the line passes through / close to all points. Mark consequentially on candidate’s graph 1

(ii) There are no anomalous points Mark consequentially on candidate’s graph 1

(f) The experiment only seeks an approximate figure for the maximum pressure Allow words to that effect. 1

(g) (i) Toxic (to marine life) Allow phrasing which implies a detrimental effect on marine ecology. 1

(ii) Mixing the effluent with (sea) water to dilute it Penalise any method which removes the salt or which implies storage. 1

– – (h) 2Br + Cl2 → 2Cl + Br2 Allow NaBr or KBr 1

Page 67 of 71 (i) The cost of removing water / heating would be too high Discount answers based on toxicity or speed of reaction. Allow answers based on cost of using sulfuric acid. 1

(j) (i) Carbon Allow C, soot, graphite, coal. 1

(ii) Formed by the decomposition of organic material / living organisms in the sea water Allow ‘erosion of coal beds’. 1

(iii) Dissolve the solid formed in water Do not allow melting of the solid. 1

Filter off the insoluble particles 1

(k) Ca(OH)2 + 2HCl → CaCl2 + 2H2O + 2+ Allow Ca(OH)2 + 2H → Ca + 2H2O Allow multiples. 1

(l) In agriculture / to raise the pH of soil / (Lime-based) mortars in construction Allow words to that effect. 1 [22]

Q30. (a) Antacid

to neutralise acidity

eases indigestion Credit suitable reference to indigestion or to laxative or to relief of constipation 1

(b) M1 Decrease in T decreases the energy of the particles/ions/H+/molecules

M2 (also scores M1) Decrease in the number of/less particles/ions/ + H /molecules with E ≥ EAct or E ≥ minimum energy to react In M1 and M2, credit “atoms” but ignore “calcium carbonate”, ignore “calcium”, ignore any ion formula except H+

M3 Few(er)/Less effective/productive/successful collisions QoL 3

Page 68 of 71 (c) (i) Strontium has a higher melting point than barium, because

Correct reference to size of cations/proximity of electrons M1 (For Sr) delocalised electrons closer to cations/positive ions/atoms/nucleus

cations/positive ions/atoms are smaller

cation/positive ion/atom or it has fewer (electron) shells/levels Ignore general Group 2 statements Penalise M1 if Sr or Ba is said to have more or less delocalised electrons Ignore reference to shielding CE = 0 for reference to molecules or intermolecular forces or covalent bonds

Relative strength of metallic bonding M2 (Sr) has stronger attraction between the cations/positive ions/ atoms/nucleus and the delocalised electrons

stronger metallic bonding (assume argument refers to Sr but accept converse argument for Ba) 2 Ignore “Van der Waals forces (between atoms)” but penalise if “between molecules”

(ii) Sr + 2H2O → Sr(OH)2 + H2 Or multiples 1

(d) 2Mg + TiCl4 → 2MgCl2 + Ti Or multiples 1 [9]

Q31. (a) Fractional distillation (under reduced pressure) 1

(b) BaSO4 insoluble / remove by filtration Do not allow answers which refer to reaction rate 1

Page 69 of 71 Q32. Add (hydrochloric) acid to the mixture; Allow correct acid eg nitric acid. 1

Filter to isolate strontium sulphate; Do not allow ‘drain’ or decant’ 1 [2]

Q33. (a) Trend: increases Wrong trend CE = 0 and in (b) 1

Reason: More electron shells OR implies more shell / sub-shells / levels 1

(b) Trend: decreases 1

Explanation: Metallic bonds weaker OR weaker attraction between ions (or nuclei) & delocalised electrons 1

Atoms (ions) larger This mark is only scored if previous mark given. CE if mention molecules, intermolecular forces ionic bonding 1

Equation for magnesium: Mg + H2O → MgO + H2 1

Equation for strontium: Sr + 2H2O → Sr(OH)2 + H2 1

(d) Formula: BaSO4 1

Use: Test for sulfate ion OR Pigment, for x-rays, barium meal, paint 1 [10]

Q34. D [1]

Q35.

Page 70 of 71 Hydroxide: solubility increases 1

Sulphate: solubility decreases [BOTH inc/dec allow 1/2]

[Allow correct solubilities of top (Mg) and bottom (Ba) cpds] 1

Add: BaCl2(aq) / Ba(NO3)2(aq) / Ba(OH)2(aq) [Not solid added] 2+ [Not Ba / Ba / Ba + HCl / Pb(NO3)2(aq)]

[If BaSO4 / H2SO4 used, M3 to M6 = CE = 0] [Allow any sensible nitrate test as an alternative to the sulphate test] 1

[Note: If M3 not awarded but test would work, allow correct observations and equations]

Na2SO4 white precipitate / solid / suspension [not cloudy/milky] 1

NaNO3 no change 1

BaCl2 + Na2SO4 → BaSO4 + 2NaCl Accept ionic equation 1 [6]

Page 71 of 71

Name: ______Group 7 exam pack

Class: ______

Date: ______

Time: 303 minutes

Marks: 264 marks

Complete minimum of:

Q7 Comments: Q14 Q16 Q31

Page 1 of 71 Q1. An aqueous solution Y is known to contain one type of group 2 metal ion and one type of negative ion.

Aqueous solutions of sulfuric acid and magnesium nitrate are added to separate samples of solution Y. The observations are shown in the table.

Solution added Observation with solution Y Sulfuric acid A white precipitate forms

Magnesium nitrate A white precipitate forms

(a) Suggest the identity of the group 2 metal ion present in solution Y.

Write an ionic equation, including state symbols, for the reaction that takes place when sulfuric acid is added to solution Y.

Group 2 metal ion ______

Ionic equation ______(2)

(b) Suggest the identity of the negative ion present in solution Y.

Write an ionic equation, including state symbols, for the reaction that takes place when magnesium nitrate is added to solution Y.

Negative ion ______

Ionic equation ______(2) (Total 4 marks)

Q2. Which is the best technique to remove the silver chloride that forms when aqueous solutions of silver nitrate and sodium chloride react?

A Refluxing

B Evaporation

C Filtration

D Distillation (Total 1 mark)

Q3. Which statement about astatine is correct?

Page 2 of 71 A Astatine has a greater electronegativity than bromine

B Astatine is a better oxidising agent than bromine

C Astatine has a greater boiling point than bromine Astatine has a greater first ionisation energy than D bromine (Total 1 mark)

Q4. Which species is not produced by a redox reaction between solid sodium iodide and concentrated sulfuric acid?

A Na2SO4

B H2S

C S

D SO2

(Total 1 mark)

Q5. This question is about silver iodide.

(a) Define the term enthalpy of lattice formation.

______

______(2)

(b) Some enthalpy change data are shown in the table.

Enthalpy change

/ kJ mol−1

AgI(s) Ag+(aq) + I−(aq) +112

Ag+⟶(g) Ag+(aq) −464

I−(g) ⟶ I−(aq) −293

⟶ Use the data in the table to calculate the enthalpy of lattice formation of silver iodide.

Page 3 of 71 Enthalpy of lattice formation = ______kJ mol−1 (2)

(c) A calculation of the enthalpy of lattice formation of silver iodide based on a perfect ionic model gives a smaller numerical value than the value calculated in part (b)

Explain this difference.

______

______(2)

(d) Identify a reagent that could be used to indicate the presence of iodide ions in an aqueous solution and describe the observation made.

Reagent ______

Observation ______

______(2) (Total 8 marks)

Q6. Concentrated sulfuric acid reacts with alkenes, alcohols and sodium halides.

(a) Name the mechanism for the reaction of concentrated sulfuric acid with an alkene.

______(1)

(b) Outline the mechanism for the reaction of concentrated sulfuric acid with propene to show the formation of the major product.

(4)

Page 4 of 71

(1)

(d) Explain why the product shown in your answer to part (b) is the major product.

______

______(2)

(e) Butan-2-ol reacts with concentrated sulfuric acid to form a mixture of three isomeric alkenes. Two of the alkenes are stereoisomers.

Draw the skeletal formula of each of the three isomeric alkenes formed by the reaction of butan-2-ol with concentrated sulfuric acid.

Give the full IUPAC name of each isomer.

Skeletal formula Name

(3)

(f) A by-product of the reaction of butan-2-ol with concentrated sulfuric acid has the molecular formula C4H8O

Name this by-product, identify the role of the sulfuric acid in its formation and suggest the name of a method that could be used to separate the products of this reaction.

Page 5 of 71 By-product ______

______

Role of sulfuric acid ______

______

Name of separation method

______(3)

(g) Concentrated sulfuric acid reacts with solid sodium chloride.

Give the observation you would make in this reaction.

State the role of the sulfuric acid.

Observation with sodium chloride ______

______

Role of sulfuric acid ______

______(2)

(h) Concentrated sulfuric acid reacts with solid sodium iodide, to produce several products.

Observations made during this reaction include the formation of a black solid, a yellow solid and a gas with the smell of bad eggs.

Identify the product responsible for each observation.

Black solid ______

Yellow solid ______

Gas ______(3) (Total 19 marks)

Q7. A student was given a 50.0 g sample of solid silver chloride contaminated with solid silver carbonate. The student suggested the following method to obtain the maximum amount of pure dry silver chloride from the sample:

1. Tip the solid into a boiling tube.

2. Add dilute nitric acid.

3. Allow the remaining solid to settle.

Page 6 of 71 4. Decant off the liquid.

5. Leave the sample to dry on a shelf.

Identify any faults or omissions in the method suggested by the student. Suggest improvements to the method, using commonly available laboratory equipment.

The following chemicals are also available: distilled water, dilute solutions of NaOH, NH3, HCl, H2SO4 (Total 6 marks)

Q8. This question is about elements in Group 7 of the Periodic Table and their compounds.

(a) Bromine (Br2), strontium chloride (SrCl2) and iodine monochloride (ICl) all have similar Mr values.

Suggest, with reasons, the order of melting points for these three substances. (6)

(b) Write an equation for the reaction of chlorine with cold water.

State a reason why chlorine is added to drinking water, and suggest a disadvantage of treating water in this way.

Equation

______

Reason ______

______

Disadvantage ______

______

______(3)

Write an equation for this reaction and draw the shape of the phosphorus tribromide molecule formed.

Suggest the bond angle in phosphorus tribromide.

Equation

______

Shape

Page 7 of 71 Bond angle ______(3)

+ − (d) Phosphorus pentabromide in the solid state consists of PBr4 and Br ions.

+ Draw the shape of the PBr4 ion and suggest its bond angle.

Shape

Bond angle ______(2) (Total 14 marks)

Q9. Which equation represents a reaction that does take place?

A Cl2 + 2NaI 2NaCl + I2

B Br2 + 2NaCl⟶ 2NaBr + Cl2

⟶ C NaCl + H2O HCl + NaOH ⟶ D 2HCl + H2SO4 Cl2 + SO2 + 2H2O ⟶ (Total 1 mark)

Q10. Which species is the best oxidising agent?

A Cl2

− B Cl

C Br 2

− D Br

(Total 1 mark)

Q11. The following tests were carried out to identify an unknown green salt Y.

An aqueous solution of Y gave a cream precipitate of compound A when reacted with silver nitrate solution.

Page 8 of 71 Compound A gave a colourless solution when reacted with concentrated ammonia solution.

Another aqueous solution of Y gave a green precipitate B when reacted with sodium carbonate solution.

The green precipitate B was filtered and dried and then reacted with sulfuric acid to give a pale green solution containing compound C and a colourless gas D.

(a) Identify by name or formula the compounds A, B, C, D and Y.

Identity of A ______

Identity of B ______

Identity of C ______

Identity of D ______

Identity of Y ______(5)

(b) Write the simplest ionic equation for the reaction of silver nitrate solution with the anion that is present in compound Y.

______(1)

______(1) (Total 7 marks)

Q12. Which statement is not correct about the addition of chlorine to water?

Chlorine can react with water to form an alkaline A solution. Chlorine can react with water to produce chloride ions B and oxygen.

C Chlorine can be added to drinking water to kill bacteria. Chlorine can react with water to produce chloride ions D and chlorate(I) ions. (Total 1 mark)

Q13.

Page 9 of 71 Which of these species is the best reducing agent?

Cl2 A

− B Cl

I2 C

− D I

(Total 1 mark)

Q14. This question is about the chemical properties of chlorine, sodium chloride and sodium bromide.

(a) Sodium bromide reacts with concentrated sulfuric acid in a different way from sodium chloride.

Write an equation for this reaction of sodium bromide and explain why bromide ions react differently from chloride ions.

Equation ______

Explanation ______

______

______(3)

(b) A colourless solution contains a mixture of sodium chloride and sodium bromide.

Using aqueous silver nitrate and any other reagents of your choice, develop a procedure to prepare a pure sample of silver bromide from this mixture. Explain each step in the procedure and illustrate your explanations with equations, where appropriate.

______

Page 10 of 71 ______

______(6)

(c) Write an ionic equation for the reaction between chlorine and cold dilute sodium hydroxide solution. Give the oxidation state of chlorine in each of the chlorine-containing ions formed.

______

______(2) (Total 11 marks)

Q15. Which of these substances reacts most rapidly to produce a silver halide precipitate with acidified silver nitrate?

A CH3Br

B CH3Cl

C CH3F

D CH3l (Total 1 mark)

Q16. The table below shows observations of changes from some test-tube reactions of aqueous solutions of compounds Q, R and S with five different aqueous reagents. The initial colours of the solutions are not given.

BaCl2 + HCl AgNO3 + NaOH Na2CO3 HCl (conc) HNO3

no change pale cream white white no change Q observed precipitate precipitate precipitate observed

white white precipitate, no change white precipitate, no change R dissolves in observd precipitate bubbles of a observed excess of gas NaOH

brown white no change brown precipitate, yellow S precipitate observed precipitate bubbles of a solution gas

Page 11 of 71 (a) Identify each of compounds Q, R and S. You are not required to explain your answers.

Identity of Q ______

______

Identity of R ______

______

Identity of S ______

______(6)

(b) Write ionic equations for each of the positive observations with S.

______

______(4) (Total 10 marks)

Q17. A Grignard reagent is a compound in which magnesium is bonded to an alkyl group (R) and a halogen (X). It can be represented by the formula RMgX.

A Grignard reagent is formed by the reaction of magnesium metal with a haloalkane using dry ethoxyethane as a solvent. Ethoxyethane has a boiling point of 35 ºC, forms a dense vapour and is highly flammable.

(a) Give one reason why a hot water bath is used rather than direct heating with a Bunsen burner when preparing the Grignard reagent.

______(1)

(b) Grignard reagents react with water.

Page 12 of 71 Suggest one reason why the ethoxyethane protects the Grignard reagent from reacting with water vapour in the air.

______(1)

(c) A Grignard reagent can be used to introduce an extra carbon atom into an organic molecule. For example, propanone (CH3COCH3) reacts with CH3MgBr in a two-stage process to form 2-methylpropan-2-ol, (CH3)3COH. The isomer 2-methylpropan-1-ol is not formed in this process.

Suggest a suitable reagent and the associated observations that could be used to distinguish between 2-methylpropan-2-ol and its isomer 2-methylpropan-1-ol.

Reagent ______

Observation with 2-methylpropan-2-ol ______

______

Observation with 2-methylpropan-1-ol ______

______(3)

(d) At the end of the preparation of the alcohol, the bromine from the Grignard reagent remains as the bromide ion. Suggest reagents and observations to confirm that this halide ion is Br– and not I–

______

______(4) (Total 9 marks)

Q18. Silver cyanide can be precipitated from sodium cyanide solution by adding an excess of silver nitrate solution.

Describe how you would obtain a pure dry sample of silver cyanide from this mixture.

Page 13 of 71 ______

______

______(Total 3 marks)

Q19. A student oxidised a solution of hydrochloric acid with a few drops of sodium chlorate(l) solution. The reaction mixture effervesced and turned pale green. The gas formed bleached universal indicator paper.

(a) Write a half-equation for the oxidation of chloride ions.

______(1)

(b) Write a half-equation for the reduction of chlorate(l) ions to chlorine in acidic conditions.

______(1)

(d) A solution of sodium chlorate(l) was added to a colourless solution of potassium iodide. Suggest what is observed.

Explain the reaction that leads to this observation.

______

______(3) (Total 6 marks)

Page 14 of 71 Q20. The halogens are the elements in Group 7.

(a) The electronegativities of the halogens are shown in the table.

Halogen Fluorine Chlorine Bromine Iodine Electronegativity 4.0 3.0 2.8 2.5

Explain the trend in electronegativities shown by the halogens.

______

______(2)

(b) The halogens can all behave as oxidising agents in reactions.

(i) Explain, in terms of electron transfer, the meaning of the term oxidising agent.

______

______(1)

(ii) An equation for the reaction that takes place when chlorine gas is bubbled through aqueous potassium bromide is shown.

Cl2(g) + 2KBr(aq) → Br2(aq) + 2KCl(aq)

Explain, with reference to the oxidation states, why this is a redox reaction.

______

______(1)

(i) A sample of solid sodium iodide is reacted with concentrated sulfuric acid. A black solid forms and hydrogen sulfide gas is produced.

Write a half-equation for the reaction of sulfuric acid to form hydrogen sulfide.

______(1)

(ii) Write a half-equation for the formation of the black solid.

______

Page 15 of 71 (1)

(iii) Use your answers to parts (c) (i) and (c) (ii) to write an overall equation for the reaction of sodium iodide with concentrated sulfuric acid.

______(1)

(iv) Give the role of sulfuric acid in its reaction with sodium iodide.

Tick (✔) one box.

Acid

Oxidising agent

Reducing agent

Electrophile

(1)

(v) Write an equation for the reaction of concentrated sulfuric acid with solid sodium fluoride.

______(1)

(vi) Suggest one reason why the reaction of sodium fluoride with concentrated sulfuric acid is different from the reaction with sodium iodide.

______(1)

(d) Chlorine reacts with water to form an equilibrium mixture containing hydrochloric acid and chloric(I) acid.

(i) Write an equation for the formation of this equilibrium mixture.

______(1)

(ii) Household bleach contains sodium chlorate(I) and sodium chloride. State and explain, with reference to your equation in part (d)(i), why it is dangerous to acidify an aqueous mixture of sodium chlorate(I) and sodium chloride.

______

______(2) (Total 13 marks)

Page 16 of 71 Q21. Chlorine is an important industrial chemical.

(a) Chlorine is formed when KMnO4 reacts with hydrochloric acid. The ionic equation for this redox reaction is

+ − − 2+ 16H + 2MnO4 + 10Cl 2Mn + 8H2O + 5Cl2

(i) Deduce the half-equation for the oxidation of chloride ions to chlorine.

______(1)

− (ii) Give the oxidation state of manganese in the MnO4 ion.

______(1)

− (iii) Deduce the half-equation for the reduction of the MnO4 ions in acidified solution to manganese(II) ions and water.

______(1)

(b) Chlorine behaves as an oxidising agent in the extraction of bromine from seawater. In this process, chlorine gas is bubbled through a solution containing bromide ions.

(i) Write the simplest ionic equation for the reaction of chlorine with bromide ions.

______(1)

(ii) Give one observation that would be made during this reaction.

______

______(1)

(iii) In terms of electrons, state the meaning of the term oxidising agent.

______

______(1)

Write an equation for this reaction. Give the oxidation state of chlorine in the chlorine-containing species that is formed.

Equation

______

Oxidation state of chlorine in the species formed ______(2)

Page 17 of 71 (d) Explain why chlorine has a lower boiling point than bromine.

______

______(2) (Total 10 marks)

Q22. For many years, swimming pool water has been treated with chlorine gas. The chlorine is added to kill any harmful bacteria unintentionally introduced by swimmers. Pool managers are required to check that the chlorine concentration is high enough to kill the bacteria without being a health hazard to the swimmers.

When chlorine reacts with water in the absence of sunlight, the chlorine is both oxidised and reduced and an equilibrium is established.

(a) Write an equation for this equilibrium.

For each chlorine-containing species in the equation, write the oxidation state of chlorine below the species.

______

______(2)

(b) The pool manager maintains the water at a pH slightly greater than 7.0

Explain how this affects the equilibrium established when chlorine is added to water.

______

Page 18 of 71 (2)

______

______(2) (Total 6 marks)

Q23. This question is about Group 7 chemistry.

(a) Sea water is a major source of iodine. The iodine extracted from sea water is impure. It is purified in a two-stage process.

Stage 1 l2 + 2H2O + SO2 2Hl + H2SO4

Stage 2 2Hl + Cl2 l2 + 2HCl

(i) State the initial oxidation state and the final oxidation state of sulfur in Stage 1.

Oxidation state of S in SO2 ______

Oxidation state of S in H2SO4 ______(2)

(ii) State, in terms of electrons, what has happened to chlorine in Stage 2.

______

______(1)

(b) When concentrated sulfuric acid is added to potassium iodide, iodine is formed in the following redox equations.

...... KI + ...... H2SO4 ...... KHSO4 + ...... l2 + S + ...... H2O

8KI + 9H2SO4 8KHSO4 + 4l2 + H2S + 4H2O

(i) Balance the equation for the reaction that forms sulfur. (1)

(ii) Deduce the half-equation for the formation of iodine from iodide ions.

______(1)

Page 19 of 71 (iii) Deduce the half-equation for the formation of hydrogen sulfide from concentrated sulfuric acid.

______(1)

(c) A yellow precipitate is formed when silver nitrate solution, acidified with dilute nitric acid, is added to an aqueous solution containing iodide ions.

(i) Write the simplest ionic equation for the formation of the yellow precipitate.

______(1)

(ii) State what is observed when concentrated ammonia solution is added to this yellow precipitate.

______

______(1)

(iii) State why the silver nitrate solution is acidified when testing for iodide ions.

______

______(1)

(iv) Explain why dilute hydrochloric acid is not used to acidify the silver nitrate solution in this test for iodide ions.

______

______(1)

(d) Chlorine is toxic to humans. This toxicity does not prevent the large-scale use of chlorine in water treatment.

(i) Give one reason why water is treated with chlorine.

______

______(1)

(ii) Explain why the toxicity of chlorine does not prevent this use.

______

Page 20 of 71 ______(1)

(iii) Write an equation for the reaction of chlorine with cold water.

______(1)

(e) Give the formulas of the two different chlorine-containing compounds that are formed when chlorine reacts with cold, dilute, aqueous sodium hydroxide.

Formula 1 ______

Formula 2 ______(1) (Total 14 marks)

Q24. The following pairs of compounds can be distinguished by simple test−tube reactions.

For each pair of compounds, give a reagent (or combination of reagents) that, when added separately to each compound, could be used to distinguish between them. State what is observed in each case.

(a) Butan−2−ol and 2−methylpropan−2−ol

Reagent ______

Observation with butan−2−ol

______

Observation with 2−methylpropan−2−ol

______

______(3)

(b) Propane and propene

Reagent ______

Observation with propane

______

Observation with propene

______

Page 21 of 71 (3)

Reagent ______

Observation with aqueous silver nitrate

______

Observation with aqueous sodium nitrate

______

______(3)

(d) Aqueous magnesium chloride and aqueous barium chloride

Reagent ______

Observation with aqueous magnesium chloride

______

Observation with aqueous barium chloride

______

______(3) (Total 12 marks)

Q25. (a) Strontium chloride is used in toothpaste for sensitive teeth. Both strontium carbonate and strontium sulfate are white solids that are insoluble in water.

(i) Write an equation for the reaction between strontium chloride solution and sodium sulfate solution. Include state symbols in your equation.

______(1)

(ii) Strontium carbonate reacts with nitric acid to produce a solution of strontium nitrate. Strontium sulfate does not react with nitric acid.

Describe briefly how you could obtain strontium sulfate from a mixture of strontium carbonate and strontium sulfate. You are not required to describe the purification of the strontium sulfate.

Page 22 of 71 ______

______

______(2)

(b) A solution of magnesium sulfate is sometimes given as first aid to someone who has swallowed barium chloride.

Explain why drinking magnesium sulfate solution is effective in the treatment of barium poisoning.

______

______(1)

(c) Medicines for the treatment of nervous disorders often contain calcium bromide. Silver nitrate, acidified with dilute nitric acid, can be used together with another reagent to test for the presence of bromide ions in a solution of a medicine.

Describe briefly how you would carry out this test and state what you would observe.

______

______(3) (Total 7 marks)

Q26. The following pairs of compounds can be distinguished by simple test-tube reactions.

For each pair, give a suitable reagent that could be added separately to each compound to distinguish between them. Describe what you would observe in each case.

(a) AgBr(s) and AgI(s)

Reagent ______

Observation with AgBr(s) ______

______

Observation with AgI(s) ______

Page 23 of 71 ______(3)

(b) HCl(aq) and HNO3(aq)

Reagent ______

Observation with HCl(aq) ______

______

Observation with HNO3(aq) ______

______(3)

Reagent ______

Observation with cyclohexane ______

______

Observation with cyclohexene ______

______(3)

(d) Butanal and butanone

Reagent ______

Observation with butanal ______

______

Observation with butanone ______

______(3) (Total 12 marks)

Q27. (a) Chlorine displaces iodine from aqueous potassium iodide.

(i) Write the simplest ionic equation for this reaction.

______(1)

(ii) Give one observation that you would make when this reaction occurs.

______

Page 24 of 71 (1)

(b) In bright sunlight, chlorine reacts with water to form oxygen as one of the products. Write an equation for this reaction.

______(1)

______

(Extra space) ______

______

______(2) (Total 5 marks)

Q28. Concentrated sulfuric acid reacts with solid potassium iodide as shown in the equation.

8KI + 9H2SO4 4l2 + 8KHSO4 + H2S + 4H2O

Give two observations that you would make when this reaction occurs.

In terms of electrons, state what happens to the iodide ions in this reaction.

State the change in oxidation state of sulfur that occurs during this formation of H2S and deduce the half-equation for the conversion of H2SO4 into H2S (Total 5 marks)

Q29. Chlorine is a powerful oxidising agent.

(a) Write the simplest ionic equation for the reaction between chlorine and aqueous potassium bromide.

State what is observed when this reaction occurs.

______

Page 25 of 71 ______

______

(Extra space) ______

______(2)

(b) Write an equation for the reaction between chlorine and cold, dilute, aqueous sodium hydroxide.

Give a major use for the solution that is formed by this reaction.

Give the IUPAC name of the chlorine-containing compound formed in this reaction in which chlorine has an oxidation state of +1.

______

(Extra space) ______

______

______(3)

Give one reason why chlorine is used for the treatment of drinking water even though the gas is very toxic.

______

(Extra space) ______

______(2)

(d) State how you could test a sample of water to show that it contains chloride ions.

In your answer, give a reagent, one observation and the simplest ionic equation for

Page 26 of 71 the reaction with the reagent.

______

(Extra space) ______

______

______(3) (Total 10 marks)

Q30. A student investigated the chemistry of the halogens and the halide ions.

(a) In the first two tests, the student made the following observations.

Test Observation

1. Add chlorine water to aqueous The colourless solution turned a potassium iodide solution. brown colour.

2. Add silver nitrate solution to aqueous The colourless solution produced a potassium chloride solution. white precipitate.

(i) Identify the species responsible for the brown colour in Test 1.

Write the simplest ionic equation for the reaction that has taken place in Test 1.

State the type of reaction that has taken place in Test 1.

______

(Extra space) ______

______

Page 27 of 71 (3)

(ii) Name the species responsible for the white precipitate in Test 2.

Write the simplest ionic equation for the reaction that has taken place in Test 2.

State what would be observed when an excess of dilute ammonia solution is added to the white precipitate obtained in Test 2.

______

(Extra space) ______

______(3)

(b) In two further tests, the student made the following observations.

Test Observation

The white solid produced misty 3. Add concentrated sulfuric acid to white fumes which turned solid potassium chloride. blue litmus paper to red.

The white solid turned black. A gas 4. Add concentrated sulfuric acid to was released that smelled of rotten solid potassium iodide. eggs. A yellow solid was formed.

(i) Write the simplest ionic equation for the reaction that has taken place in Test 3.

Identify the species responsible for the misty white fumes produced in Test 3.

______

(Extra space) ______

______(2)

(ii) The student had read in a textbook that the equation for one of the reactions in Test 4 is as follows.

– 8H + 8I + H2SO4 4I2 + H2 + 4H2

Page 28 of 71 + S O

Write the two half-equations for this reaction.

State the role of the sulfuric acid and identify the yellow solid that is also observed in Test 4.

______

(Extra space) ______

______(4)

(iii) The student knew that bromine can be used for killing microorganisms in swimming pool water. The following equilibrium is established when bromine is added to cold water.

+ – Br2(I) + H2O(I) HBrO(aq) + H (aq) + Br (aq)

Use Le Chatelier’s principle to explain why this equilibrium moves to the right when sodium hydroxide solution is added to a solution containing dissolved bromine.

Deduce why bromine can be used for killing microorganisms in swimming pool water, even though bromine is toxic.

______

(Extra space) ______

______(3) (Total 15 marks)

Page 29 of 71 Q31. Iodine reacts with concentrated nitric acid to produce nitrogen dioxide (NO2).

(a) (i) Give the oxidation state of iodine in each of the following.

I2 ______

HIO3 ______(2)

(ii) Complete the balancing of the following equation.

l2 + 10HNO3 ...... HIO3 + ...... NO2 + ...... H2O (1)

(b) In industry, iodine is produced from the NalO3 that remains after sodium nitrate has been crystallised from the mineral Chile saltpetre. The final stage involves the reaction between NalO3 and Nal in acidic solution. Half-equations for the redox processes are given below.

– – + IO3 + 5e + 6H 3H2O +

l - + e–

Use these half-equations to deduce an overall ionic equation for the production of iodine by this process. Identify the oxidising agent.

Overall ionic equation

The oxidising agent ______(2)

(i) Identify the black solid.

______(1)

(ii) Deduce the half-equation for the formation of sulfur from concentrated sulfuric acid.

Page 30 of 71

______(1)

(d) When iodide ions react with concentrated sulfuric acid in a different redox reaction, the oxidation state of sulfur changes from +6 to -2. The reduction product of this reaction is a poisonous gas that has an unpleasant smell. Identify this gas.

______(1)

(e) A yellow precipitate is formed when silver nitrate solution, acidified with dilute nitric acid, is added to an aqueous solution containing iodide ions.

(ii) Write the simplest ionic equation for the formation of the yellow precipitate.

______(1)

(ii) State what is observed when concentrated ammonia solution is added to this precipitate.

______

______(1)

(iii) State why the silver nitrate is acidified when testing for iodide ions.

______

______(1)

(f) Consider the following reaction in which iodide ions behave as reducing agents.

– – Cl2(aq) + 2I (aq) I2(aq) + 2Cl (aq)

(i) In terms of electrons, state the meaning of the term reducing agent.

______

______(1)

(ii) Write a half-equation for the conversion of chlorine into chloride ions.

______

Page 31 of 71 (1)

(iii) Suggest why iodide ions are stronger reducing agents than chloride ions.

______

(Extra space) ______

______(2) (Total 15 marks)

Q32. (a) Give the formula of a Group 2 metal hydroxide used in agriculture.

______(1)

(b) Identify a sodium halide that does not undergo a redox reaction when added as a solid to concentrated sulfuric acid.

______(1)

(c) Chlorine gas reacts with cold dilute sodium hydroxide solution to form sodium chloride and another chlorine-containing compound, X.

Give the formula of X.

______(1)

(d) Give the formula of the substance responsible for the orange colour when chlorine gas is bubbled through an aqueous solution of sodium bromide.

______(1)

(e) Solid sodium iodide undergoes a redox reaction with concentrated sulfuric acid.

Give the formula for each of the following in this reaction.

Formula of the solid reduction product ______

Formula of the oxidation product ______(2)

(f) Draw the structure of each of the following organic compounds.

(i) The hydrocarbon that is a chain isomer of methylpropene, but does not exhibit

Page 32 of 71 E–Z stereoisomerism.

(1)

(ii) The alcohol that is a position isomer of butan-2-ol.

(1)

(iii) The hydrocarbon that has a peak, due to its molecular ion, at m/z = 44 in its mass spectrum.

(1)

(iv) The bromoalkane that reacts with sodium cyanide to produce propanenitrile.

(1) (Total 10 marks)

Q33. Copper(II) sulfate solution, together with copper(II) carbonate (CuCO3) powder, can be used to determine the identity of three solutions A, B and C. The three solutions are known to be hydrochloric acid, barium chloride, and sodium chloride.

In Experiment 1 a small amount of copper(II) carbonate powder was added to each of the three solutions.

In Experiment 2 a dropping pipette was used to add 2 cm3 of copper(II) sulfate solution to each of the three solutions.

Page 33 of 71 The results of these experiments are shown in the table below.

Experiment 1 Experiment 2 Addition of copper(II) Addition of copper(II) carbonate powder sulfate solution

Solution A no visible change white precipitate

Solution B no visible change no visible change

effervescence Solution C no visible change (bubbles of gas)

(a) Use the observations in the table to deduce which of the solutions, A, B or C is

hydrochloric acid ______

barium chloride ______(2)

(b) Explain why a precipitate was formed when copper(II) sulfate solution was added to solution A. Write an equation for the reaction that occurred.

Explanation ______

______

Equation ______(2)

______(1)

(d) Identify the two reagents that could be used in a test to confirm that the solutions contained chloride ions, not bromide ions. State what would be observed on addition of each reagent.

Reagent 1 ______

Observation 1 ______

______

Reagent 2 ______

Observation 2 ______

______(4)

Page 34 of 71 (e) Copper(II) sulfate is toxic. Suggest one safety precaution you would take to minimise this hazard when wiping up a spillage of copper(II) sulfate solution.

______(1) (Total 10 marks)

Q34. The presence of halide ions in solution can be detected by adding silver nitrate solution and dilute nitric acid.

(a) State the purpose of the nitric acid in this test.

______

______(1)

(b) Explain how the addition of an ammonia solution can be used to confirm that a precipitate is silver bromide.

______

______(2) (Total 3 marks)

Q35. Reactions that involve oxidation and reduction are used in a number of important industrial processes.

(a) Iodine can be extracted from seaweed by the oxidation of iodide ions. In this extraction, seaweed is heated with MnO2 and concentrated sulfuric acid.

(i) Give the oxidation state of manganese in MnO2

______(1)

2+ (ii) Write a half-equation for the reaction of MnO2 in acid to form Mn ions and water as the only products.

______(1)

(iii) In terms of electrons, state what happens to the iodide ions when they are oxidised.

______

______(1)

Page 35 of 71 (b) Chlorine is used in water treatment. When chlorine is added to cold water it reacts to form the acids HCl and HClO The following equilibrium is established.

+ – Cl2(aq) + H2O(I) H (aq) + Cl (aq) + HClO(aq)

(i) Give the oxidation state of chlorine in Cl2 and in HClO

Cl2 ______

HClO ______(2)

(ii) Deduce what happens to this equilibrium as the HClO reacts with bacteria in the water supply. Explain your answer.

______

______(2)

(c) Concentrated sulfuric acid is reduced when it reacts with solid potassium bromide. Concentrated sulfuric acid is not reduced when it reacts with solid potassium chloride.

(i) Write the two half-equations for the following redox reaction.

+ – 2H + 2Br + H2SO4 Br2 + SO2 + 2H2O

Half-equation 1

______

Half-equation 2

______(2)

(ii) Write an equation for the reaction of solid potassium chloride with concentrated sulfuric acid.

______(1)

(iii) Explain why chloride ions are weaker reducing agents than bromide ions.

______

Page 36 of 71 ______

______(2) (Total 12 marks)

Page 37 of 71 Mark schemes

Q2. C [1]

Q3. C [1]

Q4. A [1]

Q5. (a) Enthalpy change or heat energy change when 1 mol of solid ionic compound/substance or 1 mol of ionic lattice 1 is formed from its gaseous ions. 1 Allow: enthalpy change for: M+ (g) + X− (g) → MX (s) or Ag+ (g) + I− (g) → AgI (s) CE=0/2 if describing wrong process (e.g. ΔH of lattice dissociation or ΔH of formation / or heat energy required) Ignore heat energy released

(b) lattice dissociation energy= (112 + 464 + 293 ) = + 869 (kJmol−1) 1

lattice formation energy = − 869 (kJ mol −1) (+)869 = 1 mark 1

Page 38 of 71 (c) AgI contains covalent character CE=0/2 if atoms/molecules For M1, allow the following: not completely ionic / ions not spherical / ions distorted / some covalent bonding 1 Forces / bonds (holding the lattice together) are stronger Ignore covalent bonds stronger (than ionic bonds) Ignore electronegativity Ignore references to energy 1

(d) AgNO3 yellow ppt Ignore ammonia/acidified/nitric acid/sulfuric acid 1

Cl2 or Br2 brown solution/black ppt M2 dependent on correct M1 but mark on from Ag+ or Tollens 1 [8]

Q6. (a) electrophilic addition ALLOW phonetic e.g. electrophylic, electrophillic 1

(b)

M1: must show an arrow from = of C=C towards the H atom of the H–O bond or HO that is part of H–O–S–… on a compound with molecular formula H2SO4 M1 could have arrow to H+ in which case M2 would be for an independent H–O bond break on a compoundwith formula H2SO4 + ALLOW CH3–C etc for carbocation No need for hydrogensulfate to be displayed

If H2O used as electrophile – max M3 ONLY M2: must use an arrow to show the breaking of the H–O bond M2 ignore partial charges unless wrong M3: is for the correct carbocation structure NOT M3 if primary carbocation shown.

M4: must show an arrow from a lone pair of electrons on the correct oxygen of the negatively charged ion towards the positively charged carbon atom

Page 39 of 71 M4 NOT HSO4 − credit as shown (or :OSO2OH)

or as :OSO3H – in which case negative charge can be shown anywhere

ecf from H2SO3 in M1 NB: The arrows are double-headed IGNORE subsequent use of water to hydrolyse hydrogensulfate 4

ecf from 1° in (b) for CH3CH(OSO3H)CH3 ecf from alcohol as product in (b)

ecf from side chain such as –OHSO3 or –HSO4 in (b) 1

(d) (major) product formed via more stable carbocation OR secondary carbocation more stable (than primary) 1

Due to electron-releasing character / (positive) inductive effect of two alkyl / methyl groups (as opposed to one) 1 ALLOW ‘more’ alkyl groups in place of ‘two’ alkyl groups

(e)

matching name and formula for each mark One ‘salvage’ mark available for 3 correct structures or 3 correct names if no other mark awarded use of trans and cis can score 1/2 for the two but-2-ene structures 3

(f) butanone ALLOW butan-2-one 1

oxidising agent ALLOW electron acceptor but NOT electron pair acceptor 1

(fractional) distillation ALLOW gas chromatography 1

(g) white / misty / steamy fumes NOT gas evolved / effervescence 1

Page 40 of 71 acid/proton donor 1

(h) iodine / I2 IGNORE state symbols 1

sulfur / S / S8 If name and formula given they must both be right 1

hydrogen sulfide / H2S 1 [19]

Q7. This question is marked using levels of response. Refer to the Mark Scheme Instructions for Examiners for guidance on how to mark this question.

Level 3

All stages are covered and the explanation of each stage is generally correct and virtually complete.

Stage 2 is supported by correct equations.

Answer communicates the whole process coherently and shows a logical progression from stage 1 to stage 2 and then stage 3. The steps in stage 3 are in a logical order. 5-6 marks

Level 2

All stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies OR two stages are covered and the explanations are generally correct and virtually complete.

Answer is mainly coherent and shows a progression through the stages. Some steps in each stage may be out of order and incomplete. 3-4 marks

Level 1

Two stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies, OR only one stage is covered but the explanation is generally correct and virtually complete.

Answer includes some isolated statements, but these are not presented in a logical order or show confused reasoning. 1-2 marks

Level 0

Insufficient correct chemistry to warrant a mark. 0 marks Indicative Chemistry content Stage 1 Apparatus • Boiling tube likely to be too small for 50.0 g solid plus

Page 41 of 71 acid • Use a (large / medium / 250 ml) beaker instead Stage 2 AgCl Prep

• HNO3 will form soluble AgNO3 so max AgCl not obtained • Use HCl instead • Method doesn’t say how much acid should be used Or Use excess acid / Add acid until no more bubbles evolved Stage 3 Making pure dry solid

• Decanting means solid wet / contaminated with HNO3 / acid or decanting means some solid lost • Instead use filter and then wash with distilled water (and then dry) [6]

Q8. (a) SrCl2> ICl > Br> If wrong can award 1 for one in the correct ‘position’ 2

SrCl2 strong ionic bonds / (strong electrostatic attraction between opposite ions) 1

Lattice so many strong bonds to overcome 1

ICl has dipole-dipole between molecules – weaker than ionic bonds 1

Br2 has van der Waals forces between molecules – much weaker Accept London / dispersion / induced dipole forces 1

(b) Cl2 + H2O HCl + HClO

OR 2Cl2 + 2H2O O2 + 4HCl ⇌ + − − OR Cl2 + H2O 2H + Cl + ClO ⇌ 1 ⇌ Kills bacteria 1

Wasteful as most potable water not used for drinking - used in washing clothes etc

OR Some people suffer eye irritation / Some people find the taste unpleasant

OR can react with organic compounds to produce harmful substances Allow ‘it is potentially toxic as it can be if over concentrated’ 1

Accept 4P for P4 ⟶ 1

Page 42 of 71 Pyramidal shown in a diagram (but the name of the shape isn’t needed) 1

100–108° Actual value is 101° (hence larger range of values allowed) 1

(d) Tetrahedral shown in a diagram (but the name of the shape isn’t needed) 1

109.5° Accept 109° or 109°28’ 1 [14]

Q9. A [1]

Q10. A [1]

Q11. (a) A Silver bromide / AgBr 1

B Iron(II) carbonate / FeCO3 1

C Iron(II) sulphate / FeSO4 1

D Carbon dioxide / CO2 1

Y Iron(II) bromide / FeBr2 1

(b) Ag+ + Br− AgBr Allow equation if state symbols missing but penalise if state ⟶symbols are incorrect 1

+ 2− (c) 2H + CO3 H2O + CO2 + 2+ Allow FeCO3 + 2H Fe + CO2 + H2O ⟶ 1 ⟶ [7]

Q12. A [1]

Page 43 of 71 Q13. D [1]

Q14.

(a) 2NaBr + 2H2SO4 Na2SO4 + Br2 + SO2 + 2H2O Allow ionic equation – 2– 2Br + 2H2SO4 Br2 + SO4 + SO2 + 2H2O 1

Br– ions are bigger than Cl– ions 1

Therefore Br– ions more easily oxidised / lose an electron more easily (than Cl– ions) 1

(b) This question is marked using levels of response. Refer to the Mark Scheme Instructions for Examiners for guidance on how to mark this question.

Level 3

All stages are covered and the explanation of each stage is generally correct and virtually complete. Stages 1 and 2 are supported by correct equations.

Answer communicates the whole process coherently and shows a logical progression from stage 1 to stage 2 and then stage 3. The steps in stage 3 are in a logical order. 5–6 marks

Level 2

All stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies OR two stages are covered and the explanations are generally correct and virtually complete.

Answer is mainly coherent and shows a progression through the stages. Some steps in each stage may be out of order and incomplete. 3–4 marks

Level 1

Two stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies, OR only one stage is covered but the explanation is generally correct and virtually complete.

Answer includes some isolated statements, but these are not presented in a logical order or show confused reasoning. 1–2 marks

Level 0

Insufficient correct chemistry to warrant a mark. 0 marks Indicative chemistry content Stage 1: formation of precipitates

Page 44 of 71 • Add silver nitrate • to form precipitates of AgCl and AgBr • AgNO3 + NaCl → AgCl + NaNO3 • AgNO3 + NaBr → AgBr + NaNO3 Stage 2: selective dissolving of AgCl • Add excess of dilute ammonia to the mixture of precipitates • the silver chloride precipitate dissolves + − • AgCl + 2NH3 → Ag(NH3)2 + Cl Stage 3: separation and purification of AgBr • Filter off the remaining silver bromide precipitate • Wash to remove soluble compounds • Dry to remove water 6

– – – (c) Cl2 + 2HO OCl + Cl + H2O 1

OCl– is +1

Cl– is –1 Both required for the mark 1 [11]

Q15. D [1]

Q16. (a) Q is calcium or magnesium 1

bromide 1

R is aluminium 1

chloride 1

S is iron(III) 1

sulfate 1 Mark this question independently

2+ 2– (b) Ba + SO4 BaSO4 1

3+ – [Fe(H2O)6] + 3OH Fe(H2O)3(OH)3 + 3H2O 1

Page 45 of 71 3+ 2– 2[Fe(H2O)6] + 3CO3 2Fe(H2O)3(OH)3 + 3H2O + 3CO2 1

3+ – – [Fe(H2O)6] + 4Cl [FeCl4] + 6H2O 1 [10]

Q17. (a) Ethoxyethane is flammable Accept “to avoid igniting ethoxyethane vapour”. 1

(b) Ethoxyethane (vapour) forms a protective layer Water and ethoxyethane are immiscible. Do not allow ‘ethoxyethane is dense’ without further qualification. 1

Accept acidified sodium dichromate / Na2Cr2O7 1

Observation with 2-methylpropan-2-ol – no colour change M2 Accept “stays orange”. 1

Observation with 2-methylpropan-1-ol – (orange to) green M3 Accept chemically correct alternatives. 1

(d) i. (Acidified) silver nitrate (solution) Allow a chemically correct alternative reagent. 1

ii. Cream / off-white precipitate Allow this alternative with correct observation. 1

Dilute ammonia solution OR Conc ammonia solution Allow this alternative with correct confirmatory reagent or procedure. 1

some ppt dissolves or ppt dissolves Allow this alternative with correct confirmatory result. Do not allow full marks for alternatives without both a test and a confirmation. 1 [9]

Q18. Filter Must be in this order

Page 46 of 71 1

Wash (the residue) with water 1

Dry by pressing between filter paper or in air Allow other suitable methods for drying. If heat is mentioned, method of gentle heating must be specified. Heat, alone, is not sufficient 1 [3]

Q19.

− (−) (a) 2Cl → Cl2 + 2e

− (−) Allow 2Cl − 2e → Cl2 Allow correct equation forming ClO− but not Cl+ 1

− + − (b) 2ClO + 4H + 2e → Cl2 + 2H2O Allow HClO in correctly balanced equation 1

− − + (c) ClO + Cl + 2H → Cl2 + H2O

allow HClO + HCl + → Cl2 + H2O 1

(d) Goes brown (or shades of brown) Allow black ppt/solid but NOT black solution or purple 1

− Due to iodine or I3 Correct ½ equation scores M2 and M3 1

Because I− oxidised 1 [6]

Q20. (a) Increasing atomic radius / shielding / number of shells / size (down group) or reverse argument NOT ‘molecules’ 1

Decreasing attraction of nucleus/protons for shared (electron) pair / bond electrons NOT if attraction for single electron implied 1

(b) (i) Electron acceptor / species that accepts electrons / species that gains electrons NOT electron pair NOT just ‘gain of electrons’

Page 47 of 71 1

(ii) Chlorine 0 to –1 / oxidation state/number of chlorine decreases AND Bromine –1 to 0 / oxidation state/number of bromine increases Penalise if oxidised for chlorine and/or reduced for bromine Credit oxidation states if labelled on equation 1

+ (-) (c) (i) H2SO4 + 8H + 8e → H2S + 4H2O

2- + (-) ALLOW SO4 + 10H + 8e → H2S + 4H2O ALLOW fractions/multiples IGNORE state symbols 1

– (-) (ii) 2I → I2 + 2e ALLOW fractions/multiples IGNORE state symbols

- (-) ALLOW 2I - 2e →I2 1

+ - (iii) H2SO4 + 8H + 8I → H2S + 4H2O + 4I2 ALLOW

H2SO4 + 8HI → H2S + 4H2O + 4I2

2- + SO4 + 2H + 8HI → H2S + 4H2O + 4I2

2- + - SO4 + 10H + 8I → H2S + 4H2O+4I2

- - 9H2SO4 + 8I → H2S + 4H2O + 4I2 +8HSO4

9H2SO4 + 8NaI → H2S + 4H2O + 4I2 + 8NaHSO4

+ + H2SO4 + 8H + 8NaI → H2S + 4H2O + 4I2 + 8Na

- 2- 5H2SO4 + 8I → H2S+4H2O + 4I2 + 4SO4

5H2SO4 + 8NaI → H2S + 4H2O + 4I2 + 4Na2SO4 1

(iv) ‘Oxidising agent’ box ticked 1

(v) H2SO4 + 2NaF → Na2SO4 + 2HF OR

H2SO4 + NaF → NaHSO4 + HF 1

(vi) Fluoride less powerful reducing agent (than iodide) OR Fluoride less easily oxidised than iodide Or reverse argument in either case NOT general group VII trend statement NOT fluorine/F or iodine/I

Page 48 of 71 Must be comparative 1

+ - - (d) (i) Cl2 + H2O 2H + Cl + ClO /HCl + HOCl

ALLOW⇌ → for 1 ⇌ (ii) Equilibrium shifts/moves left 1

(Producing) chlorine (which) is toxic/poisonous Mark independently 1 [13]

Q21. − − (a) (i) 2Cl Cl2 + 2e Ignore state symbols Credit loss of electrons from LHS Credit multiples Do not penalise absence of charge on electron 1

(ii) +7 OR 7 OR VII OR +VII Allow Mn+7 and 7+ 1

− + − 2+ (iii) MnO4 + 8H + 5e Mn + 4H2O Ignore state symbols Credit loss of electrons from RHS Credit multiples Do not penalise absence of charge on electron 1

− − (b) (i) Cl2 + 2Br 2Cl + Br2

− − Cl2 + Br Cl + Br2 One of these two equations only Ignore state symbols 1

(ii) (Turns to) yellow / orange / brown (solution) Penalise “red / reddish” as the only colour Accept “red-brown” and “red-orange” Ignore “liquid” Penalise reference to a product that is a gas or a precipitate 1

(iii) (Chlorine) gains electron(s) / takes electron(s) / accepts electron(s) (from the bromide ions)

Page 49 of 71 OR

(Chlorine) causes another species (Br−) to lose electron(s) Penalise “electron pair acceptor” Not simply “causes loss of electrons” 1

(4H+ + 4Cl−)

M2 Oxidation state −1 Ignore state symbols Credit multiples M2 consequential on HCl or Cl− which must be the only chlorine-containing product in the (un)balanced equation. For M2 allow Cl−1 or Cl1− but not Cl− 2

(d) M1 The relative size (of the molecules / atoms)

Chlorine is smaller than bromine OR has fewer electrons / electron shells For M1 ignore whether it refers to molecules or atoms.

OR It is smaller / It has a smaller atomic radius / it is a smaller molecule / atom (or converse) CE=0 for the clip for reference to (halide) ions or incorrect statements about relative size

Ignore molecular mass and Mr

M2 How size of the intermolecular force affects energy needed Ignore shielding

The forces between chlorine / Cl2 molecules are weaker (than the forces between bromine / Br2 molecules) (or converse for bromine) OR chlorine / Cl2 has weaker / fewer / less (VdW) intermolecular forces / forces between molecules (or converse for bromine) QoL in M2 for clear reference to the difference in size of the force between molecules. Reference to Van der Waals forces alone is not enough. Penalise M2 if (covalent) bonds are broken 2 [10]

Q22. (a) Cl2 + H2O HOCl + HCl Allow the products shown as ions. 1

Cl2 = 0, HOCl = +1 and HCl = −1 1 mark for all three oxidation states correct. Allow a reaction arrow in this equation.

Page 50 of 71 Oxidation states must match the species 1

(b) Hydroxide / alkali ions react with the acids Mark independently 1

Equilibrium moves to the right 1

The health benefits outweigh the risks 1 [6]

Q23. (a) (i) M1 (+) 4 OR IV

M2 (+) 6 OR VI 2

(ii) It / Chlorine has gained / accepted electron(s)

− − Correctly balanced half-equation eg Cl2 + 2e 2Cl Credit 1 or 2 electrons but not lone pair. The idea of ‘reduction’ alone is not enough. 1

(b) (i) 6KI + 7H2SO4 6KHSO4 + 3I2 + S + 4H2O 1

− − (ii) 2I I2 + 2e

− − 8I 4I2 + 8e Ignore charge on the electron unless incorrect. Or multiples. Credit the electrons being subtracted on the LHS. Ignore state symbols. 1

+ − (iii) H2SO4 + 8H + 8e H2S + 4H2O

2− + – SO4 + 10H + 8e H2S + 4H2O Ignore charge on the electron unless incorrect. Or multiples. Credit the electrons being subtracted on the RHS. Ignore state symbols. 1

Page 51 of 71 (c) (i) Ag+ + I− AgI ONLY Ignore state symbols. Not multiples. 1

(ii) The precipitate / solid / it does not dissolve / is insoluble / remains

OR a white / cream / yellow solid / precipitate

OR stays the same

OR no (visible / observable) change

OR no effect / no reaction Ignore ‘nothing (happens)’. Ignore ‘no observation’. 1

(iii) The silver nitrate is acidified to

• react with / remove (an)ions that would interfere with the test Credit a correct reference to ions that give a ‘false positive’.

• prevent the formation of other silver precipitates / insoluble silver compounds that would interfere with the test Do not penalise an incorrect formula for an ion that is written in addition to the name.

• remove (other) ions that react with the silver nitrate If only the formula of the ion is given, it must be correct.

• react with / remove carbonate / hydroxide / sulfite (ions) Ignore ‘sulfate’. 1

(iv) HCl would form a (white) precipitate / (white) solid (with silver nitrate and this would interfere with the test) It is not sufficient simply to state either that it will interfere or simply that the ions / compounds react to form AgCl 1

(d) (i) Any one from Ignore ‘to clean water’.

• to sterilise / disinfect water Ignore ‘water purification’ and ‘germs’.

• to destroy / kill microorganisms / bacteria / microbes / pathogens Credit ‘remove bacteria etc’ / prevent algae. 1

(ii) The (health) benefit outweighs the risk

a clear statement that once it has done its job, little of it remains

Page 52 of 71 OR

used in (very) dilute concentrations / small amounts / low doses 1

(iii) Cl2 + H2O HClO + HCl

+ − − Cl2 + H2O 2H + ClO + Cl

2Cl2 + 2H2O 4HCl + O2 Credit HOCl or ClOH Or multiples. Credit other ionic or mixed representations. Ignore state symbols. 1

(e) In either order - Both required for one mark only Credit correct ionic formulae.

NaClO (OR NaOCl) and NaCl Give credit for answers in equations unless contradicted. 1 [14]

Q24. (a) M1 acidified potassium dichromate or K2Cr2O7 / H2SO4

+ OR K2Cr2O7 / H OR acidified K2Cr2O7

M2 (orange to) green solution OR goes green

Alternative using KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate or KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 colourless solution OR goes colourless

M3 (solution) remains purple or no reaction or no (observed) change

Page 53 of 71 For M1 If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark on

Credit alkaline KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green 3

(b) M1 (Shake with) Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)

M2 (stays) orange / red / yellow / brown / the same

OR no reaction OR no (observed) change

OR as alternatives

Use KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate OR KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 (stays) purple or no reaction or no (observed) change

M3 decolourised / goes colourless / loses its colour

Use iodine

M1 iodine or I2 / KI or iodine solution

M2 no change

M3 decolourised / goes colourless / loses its colour

Use concentrated sulfuric acid

M1 concentrated H2SO4

M2 no change

M3 brown For M1, it must be a whole reagent and / or correct formula For M1 penalise incorrect attempt at correct formula, but mark

Page 54 of 71 M2 and M3 With potassium manganate(VII) If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark on

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble iodide including HI

M2 yellow precipitate or yellow solid / yellow suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble bromide including HBr

M2 cream precipitate or cream solid / cream suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 NaOH or KOH or any soluble carbonate

M2 brown precipitate or brown solid / brown suspension with NaOH / KOH (white precipitate / solid / suspension with carbonate)

Page 55 of 71 Ignore “nothing (happens)” Ignore “no observation” Ignore “clear” on its own Ignore “dissolves” 3

(d) M1 Any soluble sulfate including (dilute or aqueous) sulfuric acid

M2 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

M3 white precipitate or white solid / white suspension If no reagent or incorrect reagent or insoluble sulfate in M1, CE = 0 and no marks for M1, M2 or M3

OR as an alternative

M1 NaOH or KOH

M2 white precipitate or white solid / white suspension

If M1 uses NH3 (dilute or concentrated) penalise M1 only and mark on 3 [12]

Q25. (a) (i) SrCl2(aq) + Na2SO4(aq) → SrSO4(s) + 2NaCl(aq) Allow multiples, including fractions. Allow ionic equations. Lose this mark if any of the state symbols are missing or incorrect. 1

(ii) Add nitric acid to the mixture (until in excess)

Page 56 of 71 Do not allow any suggestion that the solution is an emetic. 1

Filter (to isolate strontium sulfate) 1

(b) Insoluble barium sulfate is formed Allow ‘removes barium ions as a precipitate’. 1

Cream precipitate M2 Allow ‘off white precipitate’. 1

Q26.

(a) M1 concentrated sulfuric acid OR c(onc) H2SO 4 If no reagent or incorrect reagent in M1, CE= 0 and no marks for M2 or M3

M2 (cream solid) turns orange OR orange / red / brown fumes / gas / vapour If dilute sulfuric acid OR “aq” (alone) CE=0

M3 (yellow solid) turns black OR purple fumes / gas / vapour OR correct reference to H2S observation (eg bad egg smell)

If H2SO4 / sulfuric acid given but not stated whether dilute or concentrated, penalise M1 and mark on for M2 and M3 If incorrect formula for the acid, penalise M1 but mark M2 and M3

OR as an alternative

M1 concentrated ammonia OR c(onc) NH3

If NH3 / ammonia / aq ammonia given, but not stated as concentrated OR if dilute ammonia given, penalise M1 but

Page 57 of 71 mark on for M2 and M3 Ignore “partially” and ignore “clear” in M2

M2 (cream solid) dissolves / solution formed

M3 precipitate remains / does not dissolve / insoluble OR no reaction / no change / (yellow solid) turns to white solid If incorrect formula for ammonia, penalise M1 but mark M2 and M3 In M3 for ammonia. ignore “nothing (happens)”. ignore “no observation”. 3

(b) M1 AgNO3 OR silver nitrate OR any soluble silver salt If no reagent OR incorrect reagent in M1, CE= 0 and no marks for M2 OR M3

M2 white precipitate or white solid / white suspension An insoluble silver salt OR Tollens’ OR Ag OR ammoniacal silver nitrate or HCl / AgNO3 CE= 0 for the clip.

M3 remains colourless OR no reaction OR no (observed) change OR no precipitate For M1 Credit acidified (OR HNO3) silver nitrate for M1 and mark on. If silver ions or incorrect formula for silver nitrate, penalise M1 but mark M2 and M3

Credit alternative test for nitrate ions For M2 Ignore “cloudy solution” OR “suspension”. For M3 Ignore “nothing (happens)”. Ignore “no observation”. Ignore “clear”. Ignore “dissolves”. 3

(c) M1 Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent) If no reagent or incorrect reagent in M1, CE= 0 and no marks for M2 or M3

Either Order M2 (stays) Orange / red / yellow / brown / the same OR no reaction OR no (observed) change OR reference to colour going to cyclohexane layer No credit for combustion observations; CE=0 For M2 in every case. Ignore “nothing (happens)”. Ignore “no observation”. Ignore “clear”.

M3 decolourised / goes colourless / loses its colour With bromine (water)

Page 58 of 71 For M1, it must be a whole reagent and / or correct formula. If oxidation state given in name, it must be correct. For M1 penalise incorrect formula, but mark M2 and M3

OR as an alternative

Use KMnO4/H2SO4 M1 acidified potassium manganate(VII) or KMnO4/H2SO4 + OR KMnO4/ H OR acidified KMnO4 M2 (stays) purple or no reaction or no (observed) change With potassium manganate(VII) For M1

M3 purple to colourless solution OR goes colourless If “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 but mark M2 and M3

Credit alternative test using iodine (for M1) M2 (brown) to purple or accept no change, M3 colourless Credit alternative test using concentrated H2 SO4 M2 no change, M3 brown

Credit alkaline / neutral KMnO4 for possible full marks but M3 gives brown precipitate or solution goes green. 3

(d) M1 Tollens’ (reagent) OR ammoniacal silver nitrate OR a description of making Tollens’ (Ignore either AgNO3 or [Ag(NH3)2+] or “the silver mirror test” on their own, but mark M2 and M3) M2 silver mirror OR black solid / precipitate (Ignore silver precipitate) M3 (stays) colourless or no reaction or no (observed) change If no reagent or incorrect reagent in M1, CE= 0 and no marks for M2 or M3 For M3 in every case Ignore “nothing (happens)”. Ignore “no observation”.

Alternative using Fehling’s (solution) M1 Fehling’s (solution) or Benedict’s solution 2+ (Ignore Cu (aq) or CuSO4 on their own, but mark M2 and M3) M2 Red solid / precipitate (Credit Orange or brown solid) M3 (stays) blue or no reaction or no (observed) change With potassium dichromate(VI) For M1 If “dichromate” or “(potassium) dichromate(IV)” or incorrect formula or no acid, penalise M1 but mark M2 and M3

Alternative using K2Cr2O7/H2 SO4 M1 acidified potassium dichromate or K2Cr2O7/H2SO4 + OR K2Cr2O7/H OR acidified K2Cr2O7 M2 (Orange to) green solution OR goes green M3 (stays) Orange or no reaction or no (observed) change For M3 Ignore dichromate described as “yellow” or “red”.

Page 59 of 71 With potassium manganate(VII) For M1 If “manganate” or “(potassium manganate(IV)” or incorrect formula or no acid, penalise M1 but mark M2 and M3

Alternative using KMnO4 /H2 SO4

M1 acidified potassium manganate(VII) or KMnO4 /H2 SO 4 + OR KMnO 4 /H OR acidified KMnO 4 M2 purple to colourless solution OR goes colourless M3 (stays) purple or no reaction or no (observed) change

Credit alkaline / neutral KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green. 3 [12]

Q27. − − (a) (i) ½Cl2 + I ½ I2 + Cl Only these two equations.

− − Cl2 + 2I I2 + 2Cl 1

(ii) (Solution turns from colourless to) brown / red-brown solution Allow grey / black solid. Ignore “purple”. 1

(b) 2Cl2 + 2H2O 4HCl + O2 (4H+ + 4Cl−) Credit multiples. 1

(c) M1 The relative size (of the molecules / atoms) Chlorine is smaller than bromine OR has fewer electrons / electron shells OR It is smaller / It has a smaller atomic radius / it is a smaller molecule / or has smaller Mr (or converse for bromine) Ignore general Group 7 statements. For M1 ignore whether it refers to molecules or atoms.

M2 How size of the intermolecular force affects energy needed The forces between chlorine / Cl2 molecules are weaker (than the forces between bromine / Br2 molecules leading to less energy needed to separate the molecules) (or converse for bromine) OR chlorine / Cl2 has weaker / less / fewer forces between molecules OR chlorine / Cl2 has weaker / less / fewer intermolecular forces (or converse for bromine) CE=0 for reference to (halide) ions. QoL for clear reference to the difference in size of the force between molecules. Penalise M2 if (covalent) bonds are broken. 2

Page 60 of 71 [5]

Q28. M1 and M2 (either order)

Any two from

• purple vapour / gas

• (white solid goes to) black or black / grey or black / purple solid

• bad egg smell or words to this effect Ignore misty white fumes Ignore yellow solid Ignore purple solid Ignore “goes (dark) brown”

M3 Or multiples for possible equation in M3

The iodide ion(s) / they lose (an) electron(s)

2I− I2 + 2e−

M4 Accept “changes by − 8”

Oxidation state of S changes from +6 to −2 or changes by 8

H2SO4 + 8H+ + 8e− H2S + 4H2O

SO42− + 10H+ + 8e− H2S + 4H2O [5]

Q29.

(a) M1 Cl2 + 2Br− 2Cl− + Br2

Accept a correct equation using ½ Cl2 but no other multiples

M2 solution goes orange / yellow ( from colourless) Ignore reference to brown colour Penalise incorrect observations eg fumes, precipitates 2

(b) M1 Cl2 + 2NaOH NaClO + NaCl + H2O

Page 61 of 71 (NaOCl) Or a correct ionic equation Ignore reference to “swimming pools” and to “disinfectant”

M2 bleach or kills bacteria / bacteriacide / micro-organisms / microbes

M3 sodium chlorate(I) ONLY 3

(HOCl) Equilibrium symbol required in M1 Accept ionic RHS

The (health) benefit outweighs the risk or wtte

a clear statement that once it has done its job, little of it remains

used in (very) dilute concentrations / small amounts / low doses 2

(d) M1 Silver nitrate OR AgNO3 (with or without nitric acid) For M1 If only the formula is written then it must be correct If both the formula and the name are written then ignore incorrect attempt at the formula, but penalise an incorrect name

M2 (depends on M1)

white precipitate / white solid If the reagent is incomplete eg Ag+ ions, penalise M1 and mark on

M3 Ag+ + Cl− AgCl

Penalise both M1 and M2 for alkaline AgNO3 OR for the use of HCl to acidify the silver nitrate OR for Tollens’ reagent 3 [10]

Q30. – (a) (i) M1 iodine OR I2 OR I3 Ignore state symbols Credit M1 for “iodine solution”

– – M2 Cl2 + 2I 2Cl + I2 OR

Page 62 of 71 – – ½ Cl2 + I Cl + ½ I2 Penalise multiples in M2 except those shown – M2 accept correct use of I3

M3 redox or reduction-oxidation or displacement 3

(ii) M1 (the white precipitate is) silver chloride M1 must be named and for this mark ignore incorrect formula

M2 Ag+ + Cl – AgCl For M2 ignore state symbols Penalise multiples

M3 (white) precipitate / it dissolves

OR colourless solution Ignore references to “clear” alone 3

– 2– (b) (i) M1 H2SO4 + 2Cl 2HCl + SO4 For M1 ignore state symbols

– – OR H2SO4 + Cl HCl + HSO4 Penalise multiples for equations and apply the list principle

OR H+ + Cl– HCl

M2 hydrogen chloride OR HCl OR hydrochloric acid 2

(ii) M1 and M2 in either order For M1 and M2, ignore state symbols and credit multiples

– – M1 2I I2 + 2e

– 8I 4I2 + 8e – Do not penalise absence of charge on the electron Credit electrons shown correctly on the other side of each equation

+ – M2 H2SO4 + 8H + 8e H2S + 4H2O

2– – SO4 + 10H+ + 8e H2S + 4H2O Additional equations should not contradict

M3 oxidising agent / oxidises the iodide (ions)

electron acceptor

Page 63 of 71 M4 sulfur OR S OR S2 OR S8 OR sulphur 4

(iii) M1 The NaOH / OH– / (sodium) hydroxide reacts with / neutralises the H+ / acid / HBr (lowering its concentration)

OR a correct neutralisation equation for H+ or HBr with NaOH or with hydroxide ion Ignore reference to NaOH reacting with bromide ions Ignore reference to NaOH reacting with HBrO alone

M2 Requires a correct statement for M1

The (position of) equilibrium moves / shifts(from L to R)

• to replace the H+ / acid / HBr that has been removed / lost

• OR to increase the H+ / acid / HBr concentration

• OR to make more H+ / acid / HBr / product(s)

• OR to oppose the loss of H+ / loss of product(s)

• OR to oppose the decrease in concentration of product(s) In M2, answers must refer to the (position of) equilibrium shifts / moves and is not enough to state simply that it / the system / the reaction shifts to oppose the change.

M3 The (health) benefit outweighs the risk or wtte

a clear statement that once it has done its job, little of it remains

used in (very) dilute concentrations / small amounts / low doses 3 [15]

Q31. (a) (i) M1 0

M2 (+) 5 Accept Roman V for M2 2

(ii) I2 + 10HNO3 2HIO3 + 10NO2 + 4H2O Accept multiples 1

– + – (b) M1 IO3 + 6H + 5I 3I2 + 3H2O For M1, ignore state symbols Credit multiples

Accept 2½I2 + ½I2 as alternative to 3I2

Page 64 of 71 Electrons must be cancelled

– M2 NaIO3 OR IO3 OR iodate ions OR iodate(V) ions etc. For M2 Do not penalise an incorrect name for the correct oxidising agent that is written in addition to the formula.

Accept “the iodine in iodate ions” but NOT “iodine” alone Accept “the iodine / I in iodate ions” but NOT “iodine” alone 2

+ – (ii) H2SO4 + 6H + 6e S + 4H2O Ignore state symbols

2– – SO4 + 8H+ + 6e S + 4H2O Credit multiples Do not penalise absence of charge on the electron 1

(d) hydrogen sulfide

OR H2S

OR hydrogen sulphide 1

(e) (i) Ag+ + I – AgI ONLY Ignore state symbols No multiples 1

(ii) The (yellow) precipitate / solid / it does not dissolve / is insoluble ignore “nothing (happens)”

OR turns to a white solid ignore “no observation”

OR stays the same

OR no (visible/ observable) change

OR no effect / no reaction 1

(iii) The silver nitrate is acidified to

• react with / remove (an)ions that would interfere with the test Ignore reference to “false positive”

Page 65 of 71 • remove (other) ions that react with the silver nitrate

• react with / remove carbonate / hydroxide / sulfite (ions) If only the formula of the ion is given, it must be correct 1

(f) (i) An electron donor Penalise “electron pair donor”

OR (readily) donates / loses / releases / gives (away) electron(s) Penalise “loss of electrons” alone Accept “electron donator” 1

– – (ii) Cl2 + 2e 2Cl Ignore state symbols Do not penalise absence of charge on electron – – Credit Cl2 2Cl – 2e Credit multiples 1

(iii) For M1 and M2, iodide ions are stronger reducing agents than chloride ions, because Ignore general statements about Group VII trends or about halogen molecules or atoms. Answers must be specific

M1 Relative size of ions CE=0 for the clip if “iodine ions / chlorine ions” QoL

Iodide ions / they are larger /have more electron levels(shells) (than chloride ions) / larger atomic / ionic radius CE=0 for the clip if “iodide ions are bigger molecules / atoms” QoL

OR electron to be lost/outer shell/level (of the iodide ion) is further the nucleus

OR iodide ion(s) / they have greater / more shielding Insist on iodide ions in M1 and M2 or the use of it / they / them, in the correct context (or chloride ions in the converse argument)

OR converse for chloride ion

M2 Strength of attraction for electron(s) Must be comparative in both M1 and M2

The electron(s) lost /outer shell/level electron from (an) iodide ion(s) less strongly held by the nucleus compared with that lost from a chloride ion

OR converse for a chloride ion 2 [15]

Page 66 of 71 Q32. (a) Ca(OH)2 OR Mg(OH)2 Ignore name Could be ionic 1

(b) NaF or sodium fluoride

NaCl or sodium chloride Either formula or name can score Do not penalise the spelling “fluoride” When both formula and name are written, • penalise contradictions • if the attempt at the correct formula is incorrect, ignore it and credit correct name for the mark unless contradictory • if the attempt at the correct name is incorrect, ignore it and credit correct formula for the mark unless contradictory 1

(c) NaClO OR NaOCl Ignore name (even when incorrect) The correct formula must be clearly identified if an equation is written 1

(d) Br2 (ONLY) Only the correct formula scores; penalise lower case “b”, penalise upper case “R”, penalise superscript Ignore name The correct formula must be clearly identified if an equation is written 1

(e) M1 S OR S8 OR S2

M2 I2 (ONLY) Ignore names penalise lower case “i” for iodine, penalise superscripted numbers Mark independently The correct formula must be clearly identified in each case if an equation is written 2

(f) (i) CH3CH2CH=CH2 Structure of but-1-ene. Ignore name Credit “sticks” for C-H bonds 1

Page 67 of 71 (ii) CH3CH2CH2CH2OH Structure of butan-1-ol. Ignore name Credit “sticks” for C-H bonds 1

(iii) CH3CH2CH3 Structure of propane. Ignore name Ignore calculations and molecular formula Credit “sticks” for C-H bonds Ignore the molecular ion 1

(iv) CH3CH2Br OR C2H5Br Structure of bromoethane. Ignore name and structure of nitrile Credit “sticks” for C-H bonds 1 [10]

Q33. (a) Hydrochloric acid = C 1

Barium chloride = A 1

(b) Barium sulfate is insoluble 1

CuSO4 + BaCl2 → BaSO4 + CuCl2 Accept multiples. Accept ionic equation. Do not penalise lack of state symbols, but if used they must be correct. 1

(d) Reagent 1 silver nitrate (solution) Ignore lack of reference to acidifying prior to addition of silver nitrate solution. 1

Observation 1 White precipitate 1

Reagent 2 (dilute) ammonia solution / aqueous ammonia Do not accept addition of ammonia only. 1

Observation 2 (Colourless) solution Allow ppt dissolves. Do not allow ‘goes colourless’ or ‘goes clear’.

Page 68 of 71 Chlorine and no visible change or solution does not become orange scores M3 and M4. 1

Q34. (a) To ensure that other (an)ions do not interfere Accept ‘to prevent other salts precipitating’. Accept ‘to remove carbonate / hydroxide (ions)’. 1

(b) Concentrated (ammonia) ‘Precipitate partially soluble in dilute ammonia’ scores both marks. 1

Precipitate soluble / dissolves 1 [3]

Q35. (a) (i) MnO2 (+) 4 1

+ – 2+ (ii) MnO2 + 4H + 2e Mn + 2H2O Or multiples Ignore state symbols Credit electrons subtracted from RHS Ignore absence of charge on e 1

(iii) Iodide ion(s) is/are oxidised because they have lost electron(s) Do not penalise reference to iodine; the mark is for electron loss 1

(b) (i) M1 Cl2 0

M2 HClO (+) 1 2

(ii) M1 Equilibrium will shift/move to the right

OR L to R

OR to favour the forward reaction

Page 69 of 71 OR to produce more HClO

M2 Consequential on correct M1

To oppose the loss of HClO

OR replaces the HClO (that has reacted) for M2 NOT just “to oppose the change” 2

– – M1 2Br Br2 + 2e

+ 2– – M2 4H + SO4 + 2e SO2 + 2H2O

+ – 2H + H2SO4 + 2e SO2 + 2H2O NOT multiples Ignore state symbols Credit electrons subtracted from incorrect side Ignore absence of charge on e 2

(ii) KCl + H2SO4 KHSO4 + HCl

2KCl + H2SO4 K2SO4 + 2HCl Credit ionic equations 1

(iii) For M1 and M2, chloride ions are weaker reducing agents than bromide ions, because

M1 Relative size of ions

Chloride ions are smaller than bromide ions OR chloride ion electron(s) are closer to the nucleus OR chloride ion has fewer (electron) shells/levels OR chloride ion has less shielding (or converse for bromide ion)

M2 Strength of attraction for electron being lost

Outer shell/level electron(s) OR electron(s) lost from a chloride ion is more strongly held by the nucleus compared with that lost from a bromide ion (or converse for bromide ion) If the forces are described as intermolecular or Van der Waals then CE = 0 Ignore general reference to Group 7 trend For M1 accept reference to chlorine/bromine or reference to atoms of these but NOT “chloride/bromide atoms” or

Page 70 of 71 “chlorine/bromine molecules” For M2 insist on reference to the correct ions This is the expected answer, but award credit for a candidate who gives a correct explanation in terms of hydration enthalpy, electron affinity and atomisation enthalpy. 2 [12]

Page 71 of 71 Seven Kings High School

Haloalkanes 1 Name: ______Class: ______

Date: ______

Time: 318 minutes

Marks: 308 marks

Comments:

Complete at minimum:

Q2 – haloalkane  alkene – 13 marks Q5 – MC – 1 mark Q6 - free radicals/o zone – 13 marks Q8 – alkene – haloalkane – 12 marks Q11 – mixed - 8 marks

Total = 47 marks

Page 1 Seven Kings High School

Q1.The reaction of butane-1,4-diol with butanedioic acid produces the polymer PBS used in biodegradable packaging and disposable cutlery. Butanedioic acid is produced by two different processes.

Process 1

• Aqueous sodium hydroxide reacts with 1,4-dibromobutane to make butane-1,4-diol.

• Butane-1,4-diol is oxidised to butanedioic acid.

Process 2

• Glucose reacts with carbon dioxide in the presence of microorganisms to produce butanedioic acid directly.

• The carbon dioxide used in this process is obtained from a local factory that produces bioethanol.

(a) Deduce one safety reason and one environmental reason why Process 2 is preferred to Process 1.

......

...... (2)

(b) (i) Name and outline a mechanism for the following reaction that occurs in Process 1.

BrCH2CH2CH2CH2Br + NaOH BrCH2CH2CH2CH2OH + NaBr

......

(3)

Page 2 Seven Kings High School (ii) The infrared spectra shown are those of three compounds.

Compound A 1,4-dibromobutaneCompound B butane-1,4-diol Compound C butanedioic acid

Identify the compound responsible for each spectrum by writing the correct letter, A, B or C, in the box next to each spectrum. You may find it helpful to refer to Table 1 on the Data Sheet.

(3)

(c) In the production of bioethanol, glucose (C6H12O6) is converted into a dilute aqueous solution of ethanol and carbon dioxide.

Give the name of this process and state three essential conditions necessary to produce a good yield of ethanol. Page 3 Seven Kings High School ......

......

...... (4)

(d) State the class of alcohols to which the diol butane-1,4-diol belongs.

Identify a suitable reagent or combination of reagents for the conversion of butane-1,4-diol

into butanedioic acid (HOOCCH2CH2COOH).

Write an equation for this oxidation reaction using [O] to represent the oxidising agent.

......

...... (3) (Total 15 marks)

Q2. (a) Name and outline a mechanism for the reaction of 2-bromo-2-methylpropane with ethanolic potassium hydroxide to form the alkene 2-methylpropene, (CH3)2C=CH2

Name of mechanism ......

Mechanism

(4)

(b) Two stereoisomers of but-2-ene are formed when 2-bromobutane reacts with ethanolic potassium hydroxide.

(i) Explain what is meant by the term stereoisomers.

Page 4 Seven Kings High School ......

......

(ii) Draw the structures and give the names of the two stereoisomers of but-2-ene.

Stereoisomer 1 Stereoisomer 2

Name ...... Name ......

(iii) Name this type of stereoisomerism.

...... (5)

(c) When 2-bromo-2-methylpropane reacts with aqueous potassium hydroxide, 2-methylpropan-2-ol is formed as shown by the following equation.

State the role of the hydroxide ions in this reaction.

...... (1)

(d) Write an equation for the reaction that occurs when CH3CH2CH2CH2Br reacts with an excess of ammonia. Name the organic product of this reaction.

Equation ......

Name of product ...... (3) (Total 13 marks)

Q3.Which one of the following reactions does not involve donation of an electron pair?

+ A H + CH3NH2 → CH3NH

− B AlCl3 + Cl → A1C1

− − C CH3Cl + CN → CH3CN + Cl

Page 5 Seven Kings High School

− − D Cl2 + I → Cl + I2 (Total 1 mark)

Q4.Consider the following reaction in which an alkene is formed from a haloalkane.

(a) Name the haloalkane used in this reaction.

...... (1)

(b) Name and outline a mechanism for this reaction.

Name of mechanism ......

Mechanism

(4)

(i) State what is meant by the term structural isomers.

......

(ii) Draw the structure of this other alkene.

Page 6 Seven Kings High School

(2) (Total 7 marks)

Q5.Which one of the following statements explains best why fluoroalkanes are the least reactive haloalkanes?

A Fluorine is much more electronegative than carbon.

B The F− ion is the most stable halide ion.

C The C–F bond is the most polar carbon–halogen bond.

D The C–F bond is the strongest carbon–halogen bond. (Total 1 mark)

Q6. One of the first substances used as an anaesthetic in medicine was chloroform (trichloromethane, CHCl3). By 1950, halothane was in common use but by 1990 this had been replaced by more acceptable anaesthetics such as desflurane.

CF3CHBrCl CF3CHFOCHF2 halothane desflurane

One reason for replacing halothane was that it is an organic compound that contains chlorine. Chlorine-containing organic compounds are thought to cause damage to the ozone layer in the upper atmosphere.

(a) Name and outline a mechanism for the reaction of chlorine with methane to form

chloromethane (CH3Cl).

Write an overall equation for the reaction of chlorine with methane to form trichloromethane

(CHCl3).

......

...... (5)

(b) Explain how chlorine atoms are formed from chlorine-containing organic compounds in the Page 7 Seven Kings High School upper atmosphere.

Explain, with the aid of equations, how chlorine atoms act as a catalyst in the decomposition of ozone into oxygen.

......

...... (6)

(c) Use the formulae of the two anaesthetics, halothane and desflurane, to help to explain why desflurane is considered to be a more environmentally acceptable anaesthetic than halothane.

......

...... (2) (Total 13 marks)

Q7.How many different alkenes are formed when 2-bromo-3-methylbutane reacts with ethanolic potassium hydroxide?

A 2

B 3

C 4

D 5 (Total 1 mark)

Q8.Organic reaction mechanisms help to develop an understanding of how and why reactions occur.

(a) Propene reacts with hydrogen bromide by an electrophilic addition mechanism forming 2-bromopropane as the major product. Page 8 Seven Kings High School The equation for this reaction is shown below.

(i) Outline the mechanism for this reaction, showing the structure of the intermediate carbocation formed.

(ii) Give the structure of the alternative carbocation which could be formed in the reaction between propene and hydrogen bromide.

(5)

(b) A substitution reaction occurs when 2-bromopropane reacts with aqueous sodium hydroxide.

(i) Draw the structure of the organic product of this reaction and give its name.

Structure

Name ......

(ii) Name and outline the mechanism for this reaction.

Name of mechanism ......

Mechanism

(5)

(c) Under different conditions, 2-bromopropane reacts with sodium hydroxide to produce propene. Page 9 Seven Kings High School (i) Name the mechanism for this reaction

......

(ii) State the role of sodium hydroxide in this reaction

...... (2) (Total 12 marks)

Q9. (a) Consider the following reaction.

(i) Name and outline a mechanism for this reaction.

Name of mechanism ......

Mechanism

(3)

(ii) Name the haloalkane in this reaction.

...... (1)

(iii) Identify the characteristic of the haloalkane molecule that enables it to undergo this type of reaction.

...... (1)

(b) An alternative reaction can occur between this haloalkane and potassium hydroxide as shown by the following equation.

Name and outline a mechanism for this Page 10 reaction. Seven Kings High School Name of mechanism ......

Mechanism

(4)

...... (1)

(d) Alkenes can be polymerised to produce poly(alkenes).

(i) State the type of polymerisation that alkenes undergo.

...... (1)

(ii) Name the alkene that gives a polymer with the repeating unit shown below.

Name of alkene ...... (1) (Total 12 marks)

Q10.2-bromo-2-methylpentane is heated with potassium hydroxide dissolved in ethanol. Two structural isomers are formed.

(a) State the meaning of the term structural isomers.

......

...... (1)

(b) Name and draw the mechanism for the formation of one of the isomers.

Name of mechanism ......

Mechanism Page 11 Seven Kings High School

(5) (Total 6 marks)

Q11. Nucleophiles react with bromoethane in substitution reactions. This type of reaction is illustrated in the following scheme.

(a) State what is meant by the term nucleophile.

...... (1)

(b) Outline a mechanism for the reaction of potassium cyanide with bromoethane (Reaction 1).

(2)

......

...... (1)

(d) When potassium hydroxide reacts with bromoethane, ethene can also be formed. Name and outline a mechanism for this Page 12 reaction. Seven Kings High School Name of mechanism ......

Mechanism

(4) (Total 8 marks)

Q12. A student carried out an experiment to study the rates of hydrolysis of some haloalkanes.

(a) In the experiment, two different haloalkanes were placed in separate test tubes containing silver nitrate solution. The haloalkanes reacted with the water in the silver nitrate solution. The student timed how long it took for the first appearance of the silver halide precipitate in each tube at a constant temperature. This time was used to provide a measure of the initial rate of reaction. The student obtained the following results.

1-bromobutane 1-iodobutane

Time to form a precipitate / s 480 15

(i) State the meaning of the term hydrolysis.

......

...... (1)

(ii) State the colour of the precipitate formed when iodide ions react with silver nitrate and write the simplest ionic equation for this reaction.

Colour of precipitate ......

Simplest ionic equation

...... (2)

(iii) Use your knowledge of the reactions of halide ions with silver nitrate to suggest why the student did not include 1-fluorobutane in this experiment.

......

...... (2)

Page 13 Seven Kings High School (b) The student used the following enthalpy data to try to account for the different initial rates of hydrolysis of the haloalkanes used in part (a). The student deduced that the rate of hydrolysis of a haloalkane is influenced by the strength of the carbon–halogen bond in the haloalkane.

C–Br C–I

Bond enthalpy / kJ mol–1 276 238

State how the experimental evidence enabled the student to make this deduction.

......

...... (1)

(c) The student had read that the reaction of water with haloalkanes was similar to the reaction of aqueous sodium hydroxide with haloalkanes and was an example of a nucleophilic substitution reaction.

(i) State the meaning of the term nucleophile.

...... (1)

(ii) When a hydroxide ion collides with a molecule of 1-bromobutane, the following reaction occurs.

– – CH3CH2CH2CH2Br + OH → CH3CH2CH2CH2OH + Br

Outline the nucleophilic substitution mechanism for this reaction.

(2)

(d) The reaction of hydroxide ions with 2-bromo-2-methylpropane may occur by a different mechanism from the one in part (c). This different mechanism involves the formation of a carbocation.

(i) Complete the following equation by drawing the structure of the carbocation formed when the C–Br bond in 2-bromo-2-methylpropane is broken.

(1)

Page 14 Seven Kings High School (ii) Suggest one reason why this reaction occurs by a mechanism involving a carbocation, but the reaction in part (c) (ii) does not.

......

...... (1) (Total 11 marks)

Q13. A student read the following passage on the Internet.

Haloalkanes contain a polar covalent bond. The carbon atom of the polar covalent bond can be attacked by nucleophiles. Nucleophilic attack enables haloalkanes to undergo substitution reactions. A nucleophilic substitution reaction occurs when a haloalkane undergoes hydrolysis; the rate of hydrolysis of the haloalkane is influenced by the carbon–halogen bond enthalpy.

(a) Explain the meaning of each of the following terms in the information given above.

(i) nucleophile

......

...... (1)

(ii) substitution, as applied to nucleophilic substitution in a haloalkane

......

...... (1)

(iii) hydrolysis

......

...... (1)

(iv) bond enthalpy, as applied to a carbon–halogen bond.

......

...... (1)

Page 15 Seven Kings High School

(b) Outline a mechanism for the nucleophilic substitution reaction in which

2-bromopropane (CH3CHBrCH3) reacts with potassium hydroxide to form propan-2-ol.

(2)

(i) Outline a mechanism for the elimination reaction in which 2-bromopropane reacts with potassium hydroxide to form propene.

(3)

(ii) A student obtained the following infrared spectrum for the product from this elimination reaction.

Use information from the infrared spectrum to state and explain how the student deduced that the product was an alkene. You may find it helpful to refer to Table 1 on the Data Sheet.

......

Page 16 Seven Kings High School ......

......

...... (2) (Total 11 marks)

Q14. Oxygen and ozone (O3) both occur as gases in the upper atmosphere. Chlorine atoms catalyse the decomposition of ozone and contribute to the formation of a hole in the ozone layer.

These chlorine atoms are formed from chlorofluorocarbons (CFCs) such as CF3Cl

(a) (i) Give the IUPAC name of CF3Cl

...... (1)

(ii) Complete the following equation that shows the formation of a chlorine atom from a

molecule of CF3Cl

(1)

(iii) State what the • represents in Cl•

...... (1)

(b) Write two equations that show how chlorine atoms catalyse the decomposition of ozone into oxygen.

Equation 1 ......

Equation 2 ...... (2)

–1 3O2(g) 2O3(g) ΔH = +284 kJ mol

(i) State Le Chatelier’s principle.

......

...... (1)

(ii) Use Le Chatelier’s principle to explain how an increase in temperature causes an increase in the equilibrium yield of ozone.

...... Page 17 Seven Kings High School ......

......

...... (2)

(d) Chemists supported the legislation to ban the use of CFCs. Modern refrigerators use pentane rather than CFCs as refrigerants. With reference to its formula, state why pentane is a more environmentally acceptable refrigerant.

......

...... (1) (Total 9 marks)

Q15. Organic reaction mechanisms help chemists to understand how the reactions of organic compounds occur. The following conversions illustrate a number of different types of reaction mechanism.

(a) When 2-bromopentane reacts with ethanolic KOH, two structurally isomeric alkenes are formed.

(i) Name and outline a mechanism for the conversion of 2-bromopentane into pent-2-ene as shown below.

(4)

(ii) Draw the structure of the other structurally isomeric alkene produced when 2-bromopentane reacts with ethanolic KOH.

(1)

Page 18 Seven Kings High School (b) Name and outline a mechanism for the following conversion.

(5)

(5) (Total 15 marks)

Q16.Alkenes are useful intermediates in the synthesis of organic compounds.

(a) (i) Complete the elimination mechanism by drawing appropriate curly arrows.

Page 19 Seven Kings High School (3)

(ii) Draw structures for the E and Z stereoisomers of hex-3-ene.

E isomer of hex-3-ene Z isomer of hex-3-ene

(2)

(iii) State the meaning of the term stereoisomers.

......

(Extra space) ......

...... (2)

(b) The equation for the first reaction in the conversion of hex-3-ene into hexan-3-ol is shown below.

CH3CH2CH=CHCH2CH3 + H2SO4 CH3CH2CH2CH(OSO2OH)CH2CH3

Outline a mechanism for this reaction.

(4) (Total 11 marks)

Page 20 Seven Kings High School

Q17.Three different ways of producing ethanol are shown below.

(a) Reaction 1 produces a 15% aqueous solution of ethanol. It is claimed that the ethanol produced in this way is a carbon-neutral biofuel.

Write an equation for Reaction 1 and name the process.

Write an equation for the complete combustion of ethanol.

Explain why the ethanol produced by this process may not be a carbon-neutral biofuel.

......

(Extra space) ......

......

...... (5)

Page 21 Seven Kings High School (b) Give a reagent and conditions for Reaction 2.

CH3CH2Br CH3CH2OH

Name and outline a mechanism for Reaction 2.

Suggest one reason, other than safety, why this method is not used in industry to make ethanol.

......

(Extra space) ......

......

...... (6)

H2C =CH2 CH3CH2OH

Page 22 Seven Kings High School

Identify a suitable catalyst for Reaction 3.

Identify the type of reaction.

Give two conditions, in addition to the presence of a catalyst, necessary for Reaction 3 to produce a high yield of ethanol.

......

(Extra space) ......

......

...... (4) (Total 15 marks)

Q18.The refrigerant R410A, used in air conditioners, is a mixture of two fluoroalkanes, pentafluoroethane and difluoromethane.

(a) (i) The mechanism for the reaction of fluorine with either an alkane or a fluoroalkane is similar to that for the reaction of chlorine with methane.

Name the type of mechanism for the reaction of chlorine with methane.

...... (1)

(ii) Write equations for the following steps in the mechanism for the reaction of fluorine

with fluoromethane (CH3F) to form difluoromethane (CH2F2).

Initiation step

......

First propagation step

Page 23 Seven Kings High School ......

Second propagation step

......

A termination step leading to the formation of 1,2-difluoroethane.

...... (4)

(iii) Write an overall equation for the reaction of fluorine with ethane to form

pentafluoroethane (CF3CHF2) by this mechanism.

...... (1)

(b) The refrigerant R112A (CCl3CF2Cl) has been banned because of concerns about ozone depletion.

Give the IUPAC name for CCl3CF2Cl

...... (1)

(i) Write the overall equation for this decomposition.

...... (1)

(ii) Use the overall equation to deduce Step 3 in the following mechanism that shows how nitrogen monoxide catalyses this decomposition.

Step 1 O3 O + O2

Step 2 NO + O3 NO2 + O2

Step 3 ...... (1) (Total 9 marks)

Page 24 Seven Kings High School Q19.Consider the following reactions.

(a) Name and outline a mechanism for Reaction 1.

Name of mechanism ......

Mechanism

(5)

(b) Name and outline a mechanism for Reaction 2.

Name of mechanism ......

Mechanism

(5)

Page 25 Seven Kings High School (c) State the type of reaction in Reaction 3. Give the name of substance X.

......

...... (2)

(d) The haloalkane produced in Reaction 1 can be converted back into propene in an elimination reaction using ethanolic potassium hydroxide.

CH3CHBrCH3 H2C=CHCH3

Outline a mechanism for this conversion.

(3) (Total 15 marks)

Q20.Consider the following scheme of reactions.

(a) Give the IUPAC name for compound PPage 26 and that for compound Q. Seven Kings High School P ......

Q ...... (2)

(b) The conversion of P into Q in Reaction 1 uses HCl

Name and outline a mechanism for this reaction.

......

(5)

Name and outline a mechanism for this reaction.

...... (5)

(d) State the type of reaction shown by Reaction 3.

Identify a reagent for this reaction.

Give one condition necessary for a high yield of product when Q is converted into P.

......

...... (3)

(e) Hydrogen bromide (HBr) could be used in the overall conversion of P into R, instead of using HCl Hydrogen bromide is made by the reaction of NaBr with concentrated phosphoric acid. Concentrated sulfuric acid is not used to make HBr from NaBr

Write an equation for the reaction of NaBr with H3PO4 to produce HBr and Na3PO4 only.

Identify two toxic gases that are formed, together with HBr, when NaBr reacts with concentrated H2SO4 Page 27 Seven Kings High School

State the role of H2SO4 in the formation of these two toxic gases.

......

...... (4) (Total 19 marks)

Q21.In each of the following questions, you should draw the structure of the compound in the space provided.

(a) Draw the structure of the alkene that would form 1,2-dibromo-3-methylbutane when reacted with bromine.

(1)

(b) Draw the structure of the alcohol with molecular formula C4H10O that is resistant to oxidation by acidified potassium dichromate(VI).

(1)

(1) Page 28 Seven Kings High School

(d) Draw the structure of the organic product with Mr = 73, made from the reaction between 2-bromobutane and ammonia.

(1) (Total 4 marks)

Q22.Chlorine can be used to make chlorinated alkanes such as dichloromethane.

(a) Write an equation for each of the following steps in the mechanism for the reaction of

chloromethane (CH3Cl) with chlorine to form dichloromethane (CH2Cl2).

Initiation step

......

First propagation step

......

Second propagation step

......

The termination step that forms a compound with empirical formula CH2Cl.

...... (4)

(b) When chlorinated alkanes enter the upper atmosphere, carbon-chlorine bonds are broken. This process produces a reactive intermediate that catalyses the decomposition of ozone. The overall equation for this decomposition is

2O3 3O2

(i) Name the type of reactive intermediate that acts as a catalyst in this reaction.

...... (1) Page 29 Seven Kings High School

(ii) Write two equations to show how this intermediate is involved as a catalyst in them decomposition of ozone.

Equation 1......

Equation 2...... (2) (Total 7 marks)

Q23.There are many uses of halogenated organic compounds despite environmental concerns.

(a) Bromotrifluoromethane is used in fire extinguishers in aircraft. Bromotrifluoromethane is formed when trifluoromethane reacts with bromine.

CHF3 + Br2 CBrF3 + HBr

The reaction is a free-radical substitution reaction similar to the reaction of methane with chlorine.

(i) Write an equation for each of the following steps in the mechanism for the reaction of CHF3 with Br2

Initiation step

......

First propagation step

......

Second propagation step

......

A termination step

...... (4)

(ii) State one condition necessary for the initiation of this reaction.

...... (1)

(b) Bromine-containing and chlorine-containing organic compounds may have a role in the decomposition of ozone in the upper atmosphere.

(i) Draw an appropriate displayed formula in the space provided to complete the following equation to show how CBrF3 may produce bromine atoms in the Page 30 Seven Kings High School upper atmosphere.

• CBrF3 + Br

...... (1)

(ii) In the upper atmosphere, it is more likely for CBrF3 to produce bromine atoms than it is for CClF3 to produce chlorine atoms.

Suggest one reason for this.

......

...... (1)

(iii) Bromine atoms have a similar role to chlorine atoms in the decomposition of ozone. The overall equation for the decomposition of ozone is

2O3 3O2

Write two equations to show how bromine atoms (Br•) act as a catalyst in the decomposition of ozone.

Explain how these two decomposition equations show that bromine atoms behave as a catalyst.

Equation 1

......

Equation 2

......

Explanation ......

......

...... (3) (Total 10 marks)

Q24.Haloalkanes are used in the synthesis of other organic compounds.

(a) Hot concentrated ethanolic potassium hydroxide reacts with 2-bromo-3-methylbutane to form two alkenes that are structural isomers of each other. The major product Page 31 Seven Kings High School is 2-methylbut-2-ene.

(i) Name and outline a mechanism for the conversion of 2-bromo-3-methylbutane into 2-methylbut-2-ene according to the equation.

(CH3)2CHCHBrCH3 + KOH (CH3)2C=CHCH3 + KBr + H2O

Name of mechanism ......

Mechanism

(4)

(ii) Draw the displayed formula for the other isomer that is formed.

(1)

(iii) State the type of structural isomerism shown by these two alkenes.

...... (1)

(b) A small amount of another organic compound, X, can be detected in the reaction mixture formed when hot concentrated ethanolic potassium hydroxide reacts with 2-bromo-3-methylbutane. Compound X has the molecular formula C5H12O and is a secondary alcohol.

(i) Draw the displayed formula for X. (1)

(ii) Suggest one change to the reaction conditions that would increase the yield of X.

Page 32 Seven Kings High School ......

...... (1)

(iii) State the type of mechanism for the conversion of 2-bromo-3-methylbutane into X.

...... (1)

(iv) Identify one feature of this infrared spectrum of a pure sample of X that may be used to confirm that X is an alcohol. You may find it helpful to refer to Table 1 on the Data Sheet.

Wavenumber / cm−1

Feature ......

...... (1) (Total 10 marks)

Q25.Trifluoromethane (CHF3) can be used to make the refrigerant chlorotrifluoromethane(CClF3).

(a) Chlorotrifluoromethane is formed when trifluoromethane reacts with chlorine.

CHF3 + Cl2 CClF3 + HCl

The reaction is a free-radical substitution reaction similar to the reaction of methane with chlorine.

(i) Write an equation for each of the following steps in the mechanism for the reaction of

CHF3 with Cl2

Initiation step Page 33 Seven Kings High School ......

First propagation step

......

Second propagation step

......

Termination step to form hexafluoroethane

...... (4)

(ii) Give one essential condition for this reaction.

...... (1)

(b) In some refrigeration systems, CHF3 has replaced CClF3 because of concerns about ozone depletion.

(i) Identify the species formed from CClF3 that is responsible for the catalytic decomposition of ozone in the upper atmosphere.

...... (1)

(ii) Write an overall equation to represent the decomposition of ozone into oxygen.

...... (1) (Total 7 marks)

Q26.Consider the following reaction sequence starting from methylbenzene.

Page 34 Seven Kings High School (a) Name the type of mechanism for reaction 1.

...... (1)

(b) Compound J is formed by reduction in reaction 2.

(i) Give a reducing agent for this reaction.

...... (1)

(ii) Write an equation for this reaction. Use [H] to represent the reducing agent.

...... (1)

(iii) Give a use for J.

...... (1)

(c) Outline a mechanism for the reaction of bromomethane with an excess of compound J. You should represent J as RNH2 in the mechanism.

(4)

(d) Compound K (C6H5CH2NH2) is a structural isomer of J.

Explain why J is a weaker base than K.

...... Page 35 Seven Kings High School ......

......

...... (3) (Total 11 marks)

Q27.Why are fluoroalkanes unreactive?

A Fluorine is highly electronegative.

B The F– ion is very stable.

C They are polar molecules.

D The C–F bond is very strong. (Total 1 mark)

Q28.This question is about a method that can be used to prepare ethylamine.

CH3CH2Br + 2NH3 CH3CH2NH2 + NH4Br

Which statement about the reaction is not correct?

A Ethylamine is a primary amine.

B The mechanism is a nucleophilic substitution.

C Using an excess of bromoethane will prevent further

reaction to form a mixture of amine products.

D Ammonium bromide is an ionic compound.

(Total 1 mark) Page 36 Seven Kings High School

Q29.A four-step synthesis of compound T is shown.

(a) Give the reagent and conditions for Step 1. State how you could obtain a sample of the alcohol from the reaction mixture formed in Step 1.

......

...... (3)

(b) Draw the structure of compound S. For each of Steps 3 and 4, give a reagent and one condition, other than heat. (5) (Total 8 marks)

Q30.This question is about a method that can be used to prepare ethylamine.

CH3CH2Br + 2NH3 CH3CH2NH2 + NH4Br

Page 37 Seven Kings High School

Which of the curly arrows in the mechanism is not correct?

A 1

B 2

C 3

D 4

(Total 1 mark)

Q31.Two reactions of 2-bromopentane, (CH3CH2CH2CHBrCH3) are shown.

The C5H10 formed in reaction 1 exists as a mixture of three isomers, one of which is pent-1-ene. Two of the isomers are a pair of stereoisomers. All three isomers decolourise bromine.

(a) The same reagent is used in both reactions. The product is determined by the choice of conditions.

State the reagent and the conditions for each of reaction 1 and reaction 2.

State the role of the reagent in each reaction.

Name and outline the mechanism of reaction 1 for the formation of pent-1-ene.

......

Page 38 Seven Kings High School ...... (8)

(b) All three isomers of C5H10 contain the same functional group.

Draw the displayed formula of pent-1-ene.

Draw the structures of the pair of stereoisomers and give their full IUPAC names.

Explain the origin of the stereoisomerism shown.

......

...... (5)

(c) The rates of hydrolysis of two chloroalkanes can be investigated by adding aqueous silver nitrate to the chloroalkanes. During the hydrolysis reactions, chloride ions are liberated slowly. Precipitates of silver chloride are formed.

Outline a method to compare the rate of hydrolysis of 1-chlorobutane with that of 2-chlorobutane. State how the method would ensure a fair test.

......

Page 39 Seven Kings High School ......

......

...... (4) (Total 17 marks)

Q32.CCl4 is an effective fire extinguisher but it is no longer used because of its toxicity and its role in the depletion of the ozone layer. In the upper atmosphere, a bond in CCl4 breaks and reactive species are formed.

(a) Identify the condition that causes a bond in CCl4 to break in the upper atmosphere. Deduce an equation for the formation of the reactive species.

Condition ......

Equation

...... (2)

(b) One of the reactive species formed from CCl4 acts as a catalyst in the decomposition of ozone.

Write two equations to show how this species acts as a catalyst.

Equation 1

......

Equation 2

...... (2)

–4 (c) A small amount of the freon CF3Cl with a mass of 1.78 × 10 kg escaped from a refrigerator, into a room of volume 100 m3. Assuming that the freon is evenly distributed throughout the air in the room, calculate the number of freon molecules in a volume of 500 cm3. Give your answer to the appropriate number of significant figures.

The Avogadro constant = 6.02 × 1023 mol−1. Page 40 Seven Kings High School

Number of molecules = ...... (3) (Total 7 marks)

Q33.Refrigerants are substances used to cool refrigerators and freezers. Until recently, many of the compounds used as refrigerants were chlorofluorocarbons (CFCs), but these are now known to form chlorine radicals. CFCs have been phased out in many countries by international agreement.

(a) Write two equations to show how chlorine radicals react with ozone molecules in the upper atmosphere.

1 ......

2 ...... (2)

(b) Chloropentafluoroethane is a CFC that has been used as a refrigerant.

Draw its displayed formula.

(1)

Explain why 1,1,1-trifluoroethane does not lead to the depletion of the ozone in the upper atmosphere.

......

Page 41 Seven Kings High School ......

...... (1)

(d) One of the steps in the synthesis of 1,1,1-trifluoroethane (CF3CH3) is the reaction of 1,1-difluoroethane (CHF2CH3) with fluorine in a free-radical substitution reaction.

Write two equations to represent the propagation steps in this conversion of CHF2CH3 into CF3CH3

Propagation step 1

......

Propagation step 2

...... (2)

(e) A refrigerator contains 1.41 kg of 1,1,1-trifluoroethane (CF3CH3).

Calculate the number of molecules of 1,1,1-trifluoroethane in the refrigerator. Give your answer to an appropriate number of significant figures. (The Avogadro constant L = 6.022 × 1023 mol−1)

......

...... (2)

(f) There are growing concerns about the use of 1,1,1-trifluoroethane as a refrigerant as it is a greenhouse gas that absorbs some of Earth’s infrared radiation.

Give one reason why bonds in molecules such as carbon dioxide and 1,1,1-trifluoroethane absorb infrared radiation.

......

...... (1) (Total 9 marks)

Q34.Haloalkanes are used as refrigerants, solvents and anaesthetics.

(a) Trichloromethane (CHCl3) is a haloalkane that can be formed by heating a mixture of chloromethane (CH3Cl) and chlorine. Page 42 Seven Kings High School (i) Write an overall equation for the formation of trichloromethane by the reaction of chloromethane with chlorine.

...... (1)

(ii) Name the mechanism for this formation of trichloromethane.

...... (1)

(iii) Dichloromethane (CH2Cl2) is an intermediate in this formation of trichloromethane.

Write an equation for each of the following steps in the mechanism for the reaction of dichloromethane with chlorine.

Initiation step

......

First propagation step

......

Second propagation step

......

A termination step leading to the formation of a compound with formula C2H2Cl4

...... (4)

(b) Chlorotrifluoromethane (CClF3) is used as a refrigerant, but is being phased out due to concerns about ozone depletion in the upper atmosphere. In the upper atmosphere, CClF3 decomposes in the presence of UV light forming a reactive intermediate that catalyses the decomposition of ozone.

(i) Write an equation to show how CClF3 decomposes to form the reactive intermediate.

...... (1)

(ii) Write two equations to show how this reactive intermediate is involved in catalysing the decomposition of ozone.

1 ......

2 ...... (2) (Total 9 marks)

Q35.Which of the following is a correct mechanism for the formation of 2-methylbut-2-ene from 2-bromo-3-methylbutane? Page 43 Seven Kings High School

(Total 1 mark)

Q36.Pentanenitrile can be made by reaction of 1-bromobutane with potassium cyanide.

Which of these is the correct name for the mechanism of this reaction?

A Electrophilic addition

B Electrophilic substitution

C Nucleophilic addition

D Nucleophilic substitution

(Total 1 mark)

Page 44 Seven Kings High School

M1. (a) M1 Safety (in Process 1)

Sodium hydroxide / alkali is corrosive / harmful / caustic or sodium hydroxide is alkali(ne) Ignore references to chromium compounds

Bromine compounds are toxic / poisonous “Carbon-neutral” alone is insufficient for M2

M2 Environmental Ignore references to greenhouse gases

Process 2 could be used as a carbon sink / for carbon capture

uses waste / recycled CO2 / CO2 from the factory / CO2 from the bioethanol (or biofuel) production

reduces or limits the amount of CO2 released / given out (into the atmosphere)

Process 2 uses renewable glucose / renewable resource(s) 2

(b) (i) M1 nucleophilic substitution For M1, both words required

M2 must show an arrow from the lone pair of electrons on the oxygen atom of the negatively charged hydroxide ion to the C atom. Penalise M2 if covalent NaOH / KOH is used Penalise one mark from M2 or M3 if half-headed arrows are used

M3 must show the movement of a pair of electrons from the C–Br bond to the Br atom. Mark M3 independently provided it is from the original molecule Penalise M3 for formal charge on C of the C–Br or incorrect partial charges on C–Br Penalise once only for a line and two dots to show a bond.

For M2 and M3 award full marks for an SN1 mechanism Page 45 Seven Kings High School For M2 and M3, maximum 1 of 2 marks for the mechanism if wrong reactant is used. Penalise M3 if an extra arrow is drawn from the Br of the C–Br bond to, for example, K+ Accept the correct use of “sticks

NB The arrows here are double-headed 3

(ii) M1 B

M2 C

M3 A 3

Three conditions in any order for M2 to M4 Penalise “bacteria” and “phosphoric acid” using the list principle

M2 (enzymes from) yeast or zymase

M3 25°C ≤ T ≤ 42°C OR 298 K ≤ T ≤ 315 K Ignore reference to “aqueous” or “water”, “closed container”, “pressure, “lack of oxygen”, “concentration of ethanol” and “batch process” (i.e. not part of the list principle)

M4 anaerobic / no oxygen / no air OR neutral pH 4

(d) M1 primary OR 1° (alcohol) Mark independently

M2 acidified potassium or sodium dichromate For M2, it must be a whole reagent and/or correct formulae

+ OR H2SO4 / K2Cr2O7 OR H / K2Cr2O7 Do not penalise incorrect attempt at formula if name is correct or vice versa Accept phonetic spelling If oxidation state given in name, it must be correct. For M2 accept acidified potassium manganate(VII)

OR correct combination of formula and name

M3 Page 46 Seven Kings High School

HOCH2CH2CH2CH2OH + 4[O] HOOCCH2CH2COOH + 2H2O For M3 structures must be correct and not molecular formula 3 [15]

M2. (a) (base) elimination (penalise other words before ‘elimination’ e.g. nucleophilic) 1

M1: curly arrow from lone pair of electrons on oxygen of hydroxide ion (insist on a lone pair of electrons on the oxygen atom and a negative charge, but only credit this mark if the attack is to a correct H atom) 1

M2: curly arrow from the middle of the C-H bond to the middle of the C–C bond 1 (only credit this mark if the arrow originates from the correct C–H bond and if an attempt has been made at M1)

M3: curly arrow from the middle of the C–Br bond towards/alongside the Br atom (credit M3 independently unless the bond breaking is contradicted by an additional arrow) (penalise curly arrow if the C–Br has a formal positive charge) (credit full marks for an E1 mechanism, with M2 awarded for a correct curly arrow on the correct carbocation) (award a maximum of two marks for either an incorrect haloalkane or an incorrect organic product) (maximum 2 marks for use of 'sticks' for the haloalkane, unless RE from 2(b), when credit can be given)

(b) (i) M1: compounds with the same structural formula 1

M2: but the bonds/groups/atoms have different spatial arrangements or orientation or configuration/are arranged differently in space/3D (ignore reference to the same molecular formula for M1) 1

(ii) M1: correct structural representation for cis-but-2-ene and its name or its identification as the cis isomer 1 Page 47 Seven Kings High School M2: correct structural representation for trans-but-2-ene and its name or its identification as the trans isomer (accept representations which are 90° to linear) (award one mark for two correct structures but either wrong/no names) (maximum 1 mark for an incorrect alkene) 1

(iii) geometric(al) or cis-trans 1

(d) CH3CH2CH2CH2Br + 2NH3 → CH3CH2CH2CH2NH2 + NH4Br (M1 correct product)

(M2 balanced equation using 2NH3 and leading to NH4Br)

(penalise M1 for use of C4H9NH2 or for incorrect haloalkane, but allow consequent correct balancing of equation with 2 moles of ammonia) 2

(1–)butylamine (credit 1–aminobutane and butyl–1–amine) (award QoL mark for correct spelling) 1 [13]

M3.D [1]

M4.(a) 2-bromobutane; 1

(b) Elimination; (penalise “nucleophilic” OR “electrophilic” before the word “elimination”) Page 48 Seven Kings High School 1

M1: curly arrow from lone pair on oxygen of hydroxide ion to H atom on correct C-H adjacent to C-Br; (penalise M1 if KOH shown as covalent with an arrow breaking the bond) 1

M2: curly arrow from single bond of adjacent C-H to adjacent single bond C-C; (only credit M2 if M1 is being attempted to correct H atom) 1

M3: curly arrow from C-Br bond to side of Br atom; (credit M3 independently unless arrows contradict) (Credit possible repeat error from 2(c)(iii) for M3) (If the wrong haloalkane is used OR but-1-ene is produced, award MAX. 2 marks for the mechanism) (If E1 mechanism is used, give full credit in which M1 and M2 are for correct curly arrows on the correct carbocation)

(c) (i) (structural) isomers/hydrocarbons/compounds/they have the same molecular formula, but different structural formulas/different structures; 1 (penalise statements which are not expressed in good English and which do not refer clearly to structural isomers i.e. plural) (penalise statements which refer to “different (spatial) arrangements”) (credit” different displayed formulas”) (Q of L mark)

(ii) Correct structure for but-1-ene; 1 [7]

M5.D [1]

M6. (a) M1 (Free-) radical substitution Both words needed 1

M2 Cl2 → 2Cl• 1

M3 Cl• + CH4 → •CH3 + HCl 1

3 M4 Cl2 + •CH → CH3Cl + Cl• Page 49 Seven Kings High School 1

M5 CH4 + 3Cl2 → CHCl3 + 3HCl Penalise the absence of a radical dot once only Ignore termination steps except, if and only if both M3 and M4 do not score, then accept for one mark

Cl• + •CH3 → CH3Cl 1

(b) M1 UV (light)/ sunlight / light / UV radiation

M2 C–Cl or carbon-chlorine bond breakage OR homolysis of C–Cl OR equation to show a chlorine-containing organic compound forming two radicals

For M1 and M2, ignore use of Cl2, but credit UV and C–Cl bond breakage if seen 1

M3 Cl• + O3 → ClO• + O2 1

M4 ClO• + O3 → Cl• + 2O2 Ignore other equations Penalise the absence of a radical dot once only Accept radical dot anywhere on either radical. 1

M5 Any one from

• Combination 2O3 → 3O2

• Stated that Cl• / chlorine atom is regenerated / not used up

• Stated that the Cl• / chlorine atom is unaffected by the process. 1 For M5 accept Cl• on both sides of the equation

M6 Stated that the role of the Cl• / chlorine atom is to find an alternative route OR lower Ea / activation energy 1

(c) M1 Halothane contains C–Cl / Cl OR Desflurane does not contain C–Cl bonds / Cl OR Desflurane contains C–F / F as the only halogen Mark independently. For M1, credit the idea that desflurane contains C–F bonds that are difficult to break OR that halothane contains C–Cl bonds which are easy to break. Page 50 Seven Kings High School 1

M2 Desflurane / molecules that have fluorine as the only halogen, cause no damage / do not deplete / do not react with the ozone (layer) OR Halothane / chlorine-containing molecules, damage / deplete / react with the ozone (layer) 1 [13]

M7.A [1]

M8.(a) (i)

If wrong carbocation, lose structure mark If wrong alkene, lose structure mark Can still score ¾ i.e. penalise M3 Penalise M2 if polarity included incorrectly no bond between H and Br bond is shown as or 4

(ii)

CH3CH2CH2 credit secondary carbocation here if primary carbocation has been used in (i) Ignore attack on this carbocation by o 1 Page 51 Seven Kings High School

(b) (i) Structure: 1

Name: propan-2-ol Not 2-hydroxypropane 1

(ii) Name of mechanism: nucleophilic substitution (both words)

(NOT SN1 or SN2) 1

Mechanism:

penalise incorrect polarity on C-Br (M1) Credit the arrows even if incorrect haloalkane

If SN1, both marks possible 2

(ii) base OR proton acceptor NOT nucleophile 1 [12]

M9. (a) (i) Nucleophilic substitution 1

M1 must show an arrow from the lone pair of electrons on the oxygen atom of the negatively charged hydroxide ion to the central C atom. M2 must show the movement of a pair of electrons from the C-Br bond to the Br atom. Mark M2 independently. Penalise M1 if covalent KOH is used Penalise M2 for formal charge on C or incorrect partial charges Page 52 Seven Kings High School Penalise once only for a line and two dots to show a bond. Max 1 mark for the mechanism for the wrong reactant and/or “sticks” Ignore product

Award full marks for an SN1 mechanism in which M1 is the attack of the hydroxide ion on the intermediate carbocation.

(ii) 2-bromopropane ONLY 1

(iii) Polar C–Br OR polar carbon–bromine bond OR dipole on C–Br OR δ+ (δ–) C atom of carbon–bromine bond is δ+/electron deficient OR C―Br

(Credit carbon–halogen bond as an alternative to carbon–bromine bond) It must be clear that the discussion is about the carbon atom of the C–Br bond. NOT just reference to a polar molecule. Ignore X for halogen 1

(b) Elimination Credit “base elimination” but NOT “nucleophilic elimination” No other prefix. 1

M1 must show an arrow from the lone pair on oxygen of a negatively charged hydroxide ion to the correct H atom M2 must show an arrow from the correct C-H bond to the C-C bond and should only be awarded if an attempt has been made at M1 M3 is independent. Mechanism Penalise M1 if covalent KOH Penalise M3 for formal charge on C or incorrect partial charges Penalise once only for a line and two dots to show a bond. Max 2 marks for the mechanism for wrong reactant and/or “sticks” Ignore product

Award full marks for an E1 mechanism in which M2 is on the correct carbocation.

• alcohol(ic)/ethanol(ic) (solvent)

• high concentration of KOH/alkali/hydroxide concentrated Page 53 OR Seven Kings High School KOH/hydroxide Ignore “aqueous”

• high temperature or hot or heat under reflux or T = 78 to 100°C Ignore “excess” 1

(d) (i) Addition (polymerisation) ONLY Penalise “additional” 1

(ii) But-2-ene ONLY (hyphens not essential) Ignore references to cis and trans or E/Z Ignore butane 1 [12]

M10.(a) (Compounds with the) same molecular formula but different structural / displayed / skeletal formula 1

(b) (basic) elimination 1

Mechanism points:

Correct arrow from lone pair on :OH– to H on C adjacent to C–Br 1

Correct arrow from C–H bond to C–C 1

Correct arrow from C–Br bond to Br 1

Structure of chosen product 1

[6] Page 54 Seven Kings High School

M11. (a) Electron pair donor OR Species which uses a pair of electrons to form a co-ordinate / covalent bond. QoL Credit “lone pair” as alternative wording 1

(b)

M1 Must show an arrow from the lone pair of electrons on the carbon atom of the negatively charged cyanide ion to the central C atom.

M2 Must show the movement of a pair of electrons from the C-Br bond to the Br atom. Mark M2 independently.

Award full marks for an SN1 mechanism in which M1 is the attack of the cyanide ion on the intermediate carbocation. Penalise M1 if covalent KCN is used Penalise M2 for formal charge on C or incorrect partial charges Penalise once only for a line and two dots to show a bond. Max 1 mark for the wrong reactant or “sticks” 2

(c) Ethylamine / CH3CH2NH2 is a nucleophile OR Ethylamine could react further OR Ethylamine could make secondary / tertiary amines OR To make reaction with ammonia more likely OR To minimise further substitution OR The idea of releasing free amine from the salt OR The idea of removing a proton from the intermediate alkylammonium ion OR The idea that ammonia acts both initially as a nucleophile and then as a base Do not credit a simple reference to the equation or the mechanism requiring two moles of ammonia. 1Page 55 Seven Kings High School

(d) Elimination Credit “base elimination” but NOT “nucleophilic elimination” No other prefix.

M1 Must show an arrow from the lone pair on oxygen of a negatively charged hydroxide ion to the correct H atom

M2 Must show an arrow from the correct C-H bond to the C-C bond and should only be awarded if an attempt has been made at M1

M3 Is independent.

Award full marks for an E1 mechanism in which M2 is on the correct carbocation. Mechanism Penalise M1 if covalent KOH Penalise M3 for formal charge on C or incorrect partial charges Penalise once only for a line and two dots to show a bond. Max 2 marks for the mechanism for wrong reactant or “sticks” 3 [8]

M12. (a) (i) Splitting/breaking C─ X/bond(s) using/by (adding)/with water

Splitting/breaking the molecule/substance/compound using/by (adding)/with water NOT simply the reaction of/with water NOT simply the addition or adding of water. NOT the “splitting of water” Accept any halogen bond, but penalise other specified bonds 1

(ii) M1 yellow ONLY

M2 Ag+ + I– → AgI (Ag+ I–) For M1, penalise cream(y) OR white Ignore pale or light or dark (yellow) For M2, ignore state symbols 2

Page 56 Seven Kings High School (iii) M1 AgF OR silver fluoride is soluble/dissolves (in water)

M2 No result OR no precipitate OR no (visible) change would occur OR colourless solution Accept “silver flouride” Mark independently Ignore reference to C – F bond breakage in M1 Ignore “no reaction” and “nothing” 2

(b) The bond that takes less energy to break/the lower bond enthalpy (energy)/weaker bond means the precipitate/reaction/hydrolysis occurs faster/quicker/takes less time

The bond that takes more energy/the higher bond enthalpy (energy)/stronger bond means the precipitate/reaction/hydrolysis occurs slower/takes longer/takes more time Insist on comparative on both bond strength and rate of reaction 1

Forms a covalent or co-ordinate or dative bond by donating a pair of electrons 1 Answer must refer to an electron pair. Credit “lone pair” “Attracted” does not equal “donated”

(ii)

M1 must show an arrow from the lone pair of electrons on the oxygen atom of the negatively charged hydroxide ion to the central C atom.

M2 must show the movement of a pair of electrons from the C─Br bond to the Br atom. Mark M2 independently.

NB The arrows here are double-headed Penalise M1 if covalent NaOH is used Penalise M2 for formal Page 57 charge on C or incorrect Seven Kings High School partial charges Penalise once only for a line and two dots to show a bond. Max 1 mark for the wrong reactant

Award 1 mark only for C-Br bond breakage if an SN1 mechanism is used. Do not penalise the use of “sticks” 2

(d) (i) Structure of tertiary carbocation (CH3)3C+ or drawn out Insist on a full positive charge on the central C atom. Penalise a bond to the positive charge. Be lenient on vertical C-C bonds 1

(ii) Tertiary carbocation/carbonium ion (from 2-bromo-2-methylpropane) is more stable (than the primary carbocation/carbonium ion)

Primary carbocation/carbonium ion (from 2-bromo-2-methylpropane) is less stable (than the tertiary carbocation/carbonium ion) QoL Ignore reference to the alleged relative stability of haloalkanes 1 [11]

M13. (a) (i) Electron pair donor

Species which uses a pair of electrons to form a co-ordinate/covalent bond. Credit “lone pair” as alternative wording Credit “electron pair donator” 1

(ii) Replacement of the halogen (atom) (by the nucleophile)

The carbon-halogen bond/C-X breaks and a bond forms with the nucleophile or between the carbon and the nucleophile They must describe the idea of substitution in a haloalkane. Accept the idea that a nucleophile replaces the halogen which becomes a halide ion Penalise reference to “halogen molecule” and penalise the idea that the haloalkane contains a halide 1

(iii) Splitting molecules using/by water

breaking/splitting/dissociating Page 58 (C¡VX) bond(s)/using/by water Seven Kings High School NOT simply the reaction with water or simply the addition of water. Ignore “compound” 1

(iv) (Heat) energy/enthalpy required/needed/absorbed (at constant pressure) to break/split it/the (carbon-halogen) bond

(Heat) energy/enthalpy required/needed/absorbed (at constant pressure) for homolysis of the (C–X/the carbon-halogen) bond Ignore bond formation Ignore “average” 1

(b)

M1 must show an arrow from the lone pair of electrons on the oxygen atom of the negatively charged hydroxide ion to the central C atom.

M2 must show the movement of a pair of electrons from the C-Br bond to the Br atom. Mark M2 independently.

Award full marks for an SN1 mechanism in which M1 is the attack of the hydroxide ion on the intermediate carbocation. Penalise M1 if covalent KOH is used Penalise M2 for formal charge on C or incorrect partial charges Penalise once only for a line and two dots to show a bond. Max 1 mark for the wrong reactant Accept the correct use of “sticks” 2

M1 must show an arrow from the lone pair on oxygen of a negatively charged hydroxide ion to the correct H atom Page 59 Seven Kings High School M2 must show an arrow from the correct C-H bond to the C-C bond and should only be awarded if an attempt has been made at M1

M3 is independent provided it is from the original molecule

Award full marks for an E1 mechanism in which M2 is on the correct carbocation. Penalise M1 if covalent KOH Penalise M3 for formal charge on C or incorrect partial charges Penalise once only for a line and two dots to show a bond. Max 2 marks for wrong reactant Accept the correct use of “sticks” for the molecule except for the C-H being attacked 3

(ii) M1 Stated that the spectrum has an absorption/absorbance/ peak in the range 1620 cm–1 to 1680 (cm–1) or specified correctly in this range from the spectrum

M2 depends on correct range or wavenumber being specified

M2 (Infrared absorption) due to C=C OR carbon-carbon double bond QoL for correct M1 statement which includes both the word absorption (or alternative) and the correct range or wavenumber Allow “peak” OR “dip” OR “spike” OR “trough” OR “low transmittance” as alternatives for absorption. For M2 it is not sufficient simply to state that an alkene has C=C M2 could be on the spectrum Ignore reference to other absorptions 2 [11]

M14. (a) (i) chlorotrifluoromethane Spelling must be correct but do not penalise “flouro” Ignore use of 1– 1

(ii) CF3• May be drawn out with dot on C OR if as shown dot may be anywhere 1

(iii) An unpaired/non-bonded/unbonded/free/a Page 60 Seven Kings High School single/one/lone electron NOT “bonded electron” and NOT “paired electron” NOT “pair of electrons” NOT “electrons” Ignore “(free) radical” 1

(b) M1 Cl• + O3 → ClO• + O2

M2 ClO• + O3 → 2O2 + Cl• Mark independently Equations could gain credit in either position The dot can be anywhere on either radical Penalise the absence of a dot on the first occasion that it is seen and then mark on. Do not make the same penalty in the next equation, but penalise the absence of a dot on the other radical. Apply the list principle for additional equations 2

(c) (i) (If any factor is changed which affects an equilibrium), the (position of) equilibrium will shift/move so as to oppose the change.

(When a system/reaction in equilibrium is disturbed), the equilibrium shifts/moves in a direction which tends to reduce the disturbance Must refer to equilibrium Ignore reference to “system” alone A variety of wording will be seen here and the key part is the last phrase. An alternative to shift/move would be the idea of changing/altering the position of equilibrium 1

(ii) M1 The (forward) reaction/to the right is endothermic or takes in heat

OR The reverse reaction/to the left is exothermic or gives out heat

M2 The equilibrium moves/shifts to oppose the increase in temperature M2 depends on a correct statement for M1 For M2 accept The equilibrium moves/shifts • to take in heat/lower the temperature Page 61 Seven Kings High School • to promote the endothermic reaction and take in heat/ lower the temperature • to oppose the change and take in heat/lower the temperature (leading to the formation of more ozone) 2

(d) Any one of

• Pentane does not contain chlorine OR C–Cl (bond)

• Pentane is chlorine-free

• Pentane does not release chlorine (atoms/radicals) Ignore reference to F OR C–F OR halogen Ignore “Pentane is not a CFC” Ignore “Pentane is a hydrocarbon” Ignore “Pentane only contains C and H”

Ignore “Pentane is C5H12” 1 [9]

M15. (a) (i) M1 Elimination

M2 must show an arrow from the lone pair on the oxygen of a negatively charged hydroxide ion to a correct H atom

M3 must show an arrow from a C-H bond adjacent to the C-Br bond towards the appropriate C-C bond. Only award if a reasonable attempt has been made at the attack on the H atom of the appropriate adjacent C-H

M4 is independent provided it is from their original molecule Page 62 Seven Kings High School

Award full marks for an E1 mechanism in which M3 is on the correct carbocation.

N.B. These are double-headed arrows For M1, accept “Base elimination” but no other prefix. Penalise M2 if covalent KOH Penalise M4 for formal charge on C of C-Br or incorrect partial charges on C-Br Ignore other partial charges Penalise once only in any part of the mechanism for a line and two dots to show a bond. Max any 2 of 3 marks for the mechanism for wrong reactant (or wrong product if shown). Accept the correct use of “sticks” for the molecule except for the C-H being attacked 4

(ii) Structure for pent-1-ene

CH3CH2CH2CH=CH2

Penalise C3H7 Accept correct “sticks” 1

(b) M1 Electrophilic addition

M2 must show an arrow from the double bond towards the Br atom of the Br-Br molecule

M3 must show the breaking of the Br-Br bond.

M4 is for the structure of the tertiary carbocation with Br on the correct carbon atom.

Page 63 Seven Kings High School M5 must show an arrow from the lone pair of electrons on the negatively charged bromide ion towards the positively charged carbon atom.

N.B. These are double-headed arrows For M1, both words required. For the mechanism M2 Ignore partial negative charge on the double bond. M3 Penalise partial charges on Br-Br bond if wrong way and penalise formal charges Penalise once only in any part of the mechanism for a line and two dots to show a bond Max any 3 of 4 marks for the mechanism for wrong organic reactant or wrong organic product (if shown) or primary carbocation. If HBr is used, max 2 marks for their mechanism Accept the correct use of “sticks” 5

M2 must show an arrow from the lone pair of electrons on the nitrogen atom of an ammonia molecule to the C atom.

M3 must show the movement of a pair of electrons from the C-Br bond to the Br atom. M3 is independent provided it is from their original molecule

M4 is for the structure of the alkylammonium ion, which could be a condensed formula. A positive charge must be shown on/or close to, the N atom.

M5 is for an arrow from the N-H bond to the N atom.

Award full marks for an SN1 mechanism in which M2 is the attack of the ammonia on the intermediate carbocation.

N.B. These are double-headed arrows For M1, both words required. Page 64 Seven Kings High School

Penalise M2 if NH3 is negatively charged. Penalise M3 for formal charge on C or incorrect partial charges The second mole of ammonia is not essential for M5; therefore ignore any species here. Penalise once only for a line and two dots to show a bond. Max any 3 of 4 marks for the mechanism for wrong organic reactant (or wrong organic product if shown) Accept the correct use of “sticks” 5 [15]

M16. (a) (i) Penalise one mark from their total if half-headed arrows are used Penalise M3 for formal charge on C of the C-Br or incorrect partial charges on C-Br Ignore other partial charges

M1 must show an arrow from the lone pair on oxygen of a negatively charged hydroxide ion to the correct H atom Penalise once only in any part of the mechanism for a line and two dots to show a bond.

M2 must show an arrow from the correct C–H bond to the correct C–C bond. Only award if an arrow is shown attacking the H atom of the correct C–H bond in M1

M3 is independent but CE=0 if nucleophilic substitution

N.B these are double-headed arrows 3

Page 65 Seven Kings High School

(ii) Award 1 mark if both correct stereoisomers but in the wrong places Accept no other alkenes.

Be reasonably lenient on the bonds to ethyl (or to CH2CH3) since the question is about E and Z positions but penalise once only if

connection is clearly to the CH3 of CH2CH3 Accept linear structures 2

(iii) M1 (Compounds / molecules with) the same structural formula Penalise M1 if “same structure”

M2 with atoms/bonds/groups arranged differently in space Ignore references to “same molecular formula” or “same empirical formula” or any reference to “displayed formula”

OR atoms/bonds/groups that have different spatial arrangements / different orientation. Mark independently 2

(b)

M1must show an arrow from the double bond towards the H atom of the H – O bond OR HO on a compound with molecular formula for H2SO4

M1 could be to an H+ ion and M2 an independent O – H bond break on a compound with

molecular formula for H2SO4 M1 Ignore partial negative charge on the double bond.

M2 must show the breaking of the O – H bond. M2 Penalise partial charges on O – H bond if wrong way and penalise formal charges

In M2 do not penalise incorrect structures for H2SO4

M3 is for the structure of the carbocation.

M4 must show an arrow from the lone pair of electrons on the correct oxygen of the negatively charged ion towards a correct (positively charged) carbon atom.

– M4 NOT HSO4

–: For M4, credit as shown or OSO3H ONLY with the negative charge anywhere on this ion Page 66 Seven Kings High School OR correctly drawn out with the negative charge placed correctly on oxygen Penalise once only in any part of the mechanism for a line and two dots to show a bond

NB The arrows here are double-headed Max 3 of any 4 marks for wrong organic reactant or wrong organic product (if shown) Accept the correct use of “sticks” 4 [11]

M17.(a) M1 C6H12O6 2CH3CH2OH + 2CO2 (2C2H5OH) Mark independently For M1 and M3 ignore state symbols and credit multiples

For M1 and M3 penalise C2H6O once only

M2 fermentation

M3 CH3CH2OH + 3O2 2CO2 + 3H2O (C2H5OH)

M4 A specified process e.g. planting / harvesting / transport / extracting sugar / distilling ethanol solution / fertiliser production etc.

M5 The specified process uses / burns (fossil) fuel that releases CO2 For M5, “releases / increases carbon emissions” is insufficient as an

alternative to releases CO2 5

(b) M1 sodium or potassium hydroxide / NaOH / KOH Mark on to M2 from hydroxide ion

M2 depends on correct M1 Ignore OH– if KOH/ OH–

warm / heat / reflux and aqueous or (aq) or water For M2 ignore “dilute” For M2 penalise T > 100 °C

M3 nucleophilic substitution

Acidified KOH/NaOH or H2SO4 with KOH/NaOH loses M1 and M2

For M3, both words required

NB The arrows here are double-headed

M4 must show an arrow from the lone Page 67 pair of electrons on the oxygen atom of Seven Kings High School the negatively charged hydroxide ion to the C atom. Penalise M4 if covalent NaOH / KOH is used Penalise one mark from M4 or M5 if half-headed arrows are used

M5 must show the movement of a pair of electrons from the

C— Br bond to the Br atom. Mark M5 independently provided it is from their original molecule. Penalise M5 for formal charge on C of the C–Br or incorrect partial charges on C–Br Penalise once only for a line and two dots to show a bond.

For M4 and M5, award full marks for an SN1 mechanism For M4 and M5, maximum 1 of 2 marks if wrong reactant is used. Penalise M5 if an extra arrow is drawn from the Br of the C–Br bond to, for example, K+span> Do not penalise the use of “sticks”

M6 One statement from

• The yield is (very) low / not a high yield OR elimination occurs / ethene formed

• The rate of reaction slow

• Bromoethane has to be manufactured / made first

• Bromoethane is expensive For M6 ignore references to other costs and expenses 6

(c) M1 concentrated phosphoric acid / conc. H3PO4 OR concentrated sulfuric acid /conc. H2SO4 Answers in any order Ignore reference to support medium in M1

M2 hydration or (electrophilic) addition

For M3 and M4 any two from Do not apply the list principle to these three chosen criteria in M3 and M4

• Excess ethene

OR Excess steam / water / H2O

OR remove the ethanol as it forms

OR recycle the ethene

• Specified Pressure

50 atm ≤ P ≤ 100 atm

OR 5000 kPa ≤ P ≤ 10000 kPa

OR 5 MPa ≤ P ≤ 10 MPa Page 68 Seven Kings High School • HighTemperature unless they give a value that is not in the ranges given here;

OR 300 °C ≤ T ≤ 600 °C

OR 570 K ≤ T ≤ 870 K Accept a reference to “low temperature” if they specify a correct temperature range or a correct temperature in the range 4 [15]

M18.(a) (i) (Free-) radical substitution Both underlined words are required Penalise a correct answer if contradicted by an additional answer 1

(ii) Initiation

F2 2F• Penalise absence of dot once only

First propagation

F• + CH3F •CH2F + HF Penalise + or − charges every time

Second propagation

F2 + •CH2F CH2F2 + F•

Accept dot anywhere on CH2F radical Mark independently

Termination (must make 1,2-difluoroethane)2 •CH2F CH2FCH2F Use of half-headed arrows must be correct to score, but if not correct then penalise once only in this clip 4

(iii) CH3 CH3 + 5F2 CF3CHF2 + 5HF

(C2H6)(C2HF5) 1

(b) 1,1,1,2-tetrachloro-2,2-difluoroethane Accept phonetic spelling eg “fluro, cloro” Penalise “flouro” and “floro”, since QoL

1,2,2,2-tetrachloro-1,1-difluoroethane Ignore commas and hyphens 1

Page 69 Seven Kings High School

(ii) O + NO2 NO + O2 ONLY this answer and NOT multiples Ignore any radical dot on the O atom 1 [9]

M19.(a) M1 electrophilic addition For M1, both words required Accept phonetic spelling

For the mechanism M2 Ignore partial negative charge on the double bond

M2 must show an arrow from the double bond towards the H atom of the H–Br molecule M3 Penalise partial charges on H–Br bond if wrong way and penalise formal charges

M3 must show the breaking of the H–Br bond Penalise once only in any part of the mechanism for a line and two dots to show a bond

M5 must show an arrow from the lone pair of electrons on the negatively charged bromide ion towards the correct (positively charged) carbon atom Maximum any 3 of 4 marks for the mechanism for wrong (organic) reactant OR wrong organic product (if shown) OR primary carbocation Accept the correct use of sticks

NB These are double-headed arrows 5

(b) M1 Nucleophilic substitution For M1, both words required Accept phonetic spelling

Page 70 Seven Kings High School

For the mechanism

Penalise M2 if NH3 is negatively charged

M2 must show an arrow from the lone pair of electrons on the nitrogen atom of an ammonia molecule to the correct C atom Penalise M3 for formal charge on C of the C−Br or incorrect partial charges on C−Br Penalise M3 for an additional arrow from the Br to something else

M3 must show the movement of a pair of electrons from the C–Br bond to the Br atom. Mark M3 independently provided it is from their original molecule The second mole of ammonia is not essential for M5; therefore ignore any species here

M4 is for the structure of the alkylammonium ion, which could be a condensed formula. A positive charge must be shown on / or close to, the N atom Penalise once only for a line and two dots to show a bond

M5 is for an arrow from the N–H bond to the N atom Maximum any 3 of 4 marks for the mechanism for wrong organic reactant OR wrong organic product if shown

Award full marks for an SN1 mechanism in which M2 is the attack of the ammonia on the intermediate carbocation Accept the correct use of “sticks”

NB These are double-headed arrows 5

M2 poly(propene) / polypropene Penalise “condensation polymerisation” 2

(d)

Page 71 Seven Kings High School

Penalise M1 if covalent KOH

M1 must show an arrow from the lone pair on the oxygen of a negatively charged hydroxide ion to a correct H atom Penalise M3 for formal charge on C of C–Br or incorrect partial charges on C−Br.

M2 must show an arrow from a correct C–H bond adjacent to the C–Br bond to the appropriate C–C bond. Only award if an arrow is shown attacking the H atom of a correct C−H bond in M1 Ignore other partial charges Penalise once only in any part of the mechanism for a line and two dots to show a bond

M3 is independent provided it is from their original molecule, but CE=0 if nucleophilic substitution Maximum any 2 of 3 marks for wrong organic reactant

Award full marks for an E1 mechanism in which M3 is on the correct carbocation. Accept the correct use of “sticks” for the molecule except for the C– H being attacked

NB These are double-headed arrows 3 [15]

M20.(a) P 3,3−dimethylbut−1−ene OR accept 3,3−dimethylbutene Ignore absence of commas, hyphens and gaps Require correct spelling

Q 3−chloro−2,2−dimethylbutane OR accept 2−chloro−3,3−dimethylbutane In Q, “chloro” must come before “dimethyl” 2

(b) M1 Electrophilic addition

Page 72 Seven Kings High School

M2 must show an arrow from the double bond towards the H atom of HCl M3 must show the breaking of the H−Cl bond M4 is for the structure of the carbocation M5 must show an arrow from the lone pair of electrons on the negatively charged chloride ion towards the positively charged carbon atom on their carbocation.

NB The arrows here are double−headed M1 both words required For the mechanism M3 Penalise incorrect partial charge on H−Cl bond and penalise formal charges Ignore partial negative charge on the double bond. Maximum 3 of 4 marks for a correct mechanism using HBr or the wrong organic reactant or wrong organic product (if shown) or a primary carbocation Penalise once only in any part of the mechanism for a line and two dots to show a bond Credit the correct use of “sticks” For M5, credit attack on a partially positively charged carbocation structure, but penalise M4 5

M2 must show an arrow from the lone pair of electrons on the nitrogen atom of an ammonia molecule to the correct C atom M3 must show the movement of a pair of electrons from the C− Cl bond to the Cl atom. Mark M3 independently provided it is from their original molecule M4 is for the structure of the alkylammonium ion, which could be a condensed formula. A positive charge must be shown on, or close to, the N atom. M5 is for an arrow from the N−H bond to the N atom Award full marks for an SN1 mechanism in which M2 is the attack of the ammonia on the intermediate carbocation

NB These are double-headed Page 73 arrows Seven Kings High School For the mechanism

Penalise M2 if NH3 is negatively charged. Penalise M3 for formal charge on C of the C−Cl or incorrect partial charges on C−Cl Penalise M3 for an additional arrow from the Cl to something else The second mole of ammonia is not essential for M5; therefore ignore any species here Penalise once only for a line and two dots to show a bond Maximum 3 of 4 marks for the mechanism for wrong organic reactant OR wrong organic product if shown Accept the correct use of “sticks” 5

(d) M1 (base) elimination M1 Dehydrohalogenation

M2 KOH OR NaOH M3 Must be consequential on a correct reagent in M2, but if incomplete or inaccurate attempt at reagent (e.g. hydroxide ion), penalise M2 only and mark on

Any one from • high temperature OR hot OR heat / boil under reflux • concentrated • alcohol / ethanol (as a solvent) / (ethanolic conditions) M3 not “reflux” alone M3 if a temperature is stated it must be in the range 78C to 200 °C Ignore “pressure” 3

(e) M1 3NaBr + H3PO4 3HBr + Na3PO4 M1 Credit correct ionic species in the equation

M2 and M3 SO2 and Br2 identified M4 Concentrated sulfuric acid • is an oxidising agent • oxidises the bromide (ion) or Br− or NaBr or HBr • is an electron acceptor In M2 and M3 the two gases need to be identified. If equations are used using sulfuric acid and the toxic gases are not identified clearly, allow one mark for the formulas of SO2 and Br2 • apply the list principle as appropriate but ignore any reference to HBr • the marks are for identifying the two gases either by name or formula 4 [19]

Page 74 Seven Kings High School

M21.(a) Structure for 3-methylbut-1-ene

H2C=CHCH(CH3)2 Any correct structural representation. Credit “sticks” and require the double bond. 1

(b) Structure for 2-methylpropan-2-ol

(CH3)3COH Any correct structural representation. Credit “sticks”. 1

H2C=CHCH3 Any correct structural representation. Credit “sticks” and require the double bond. 1

(d) Structure for 2-aminobutane

CH3CH2CH(NH2)CH 3 Any correct structural representation. Credit “sticks”. 1 [4]

M22.(a) Initiation

Cl2 2Cl• Penalise absence of dot once only.

First propagation

Cl• + CH3Cl •CH2Cl + HCl Credit the dot anywhere on the radical.

Second propagation Cl2 + •CH2Cl CH2Cl2 + Cl•

Termination (must make 1,2-dichloroethane) 2 •CH2Cl CH2ClCH2Cl Page 75 Seven Kings High School

Penalise C2H4Cl2 4

(b) (i) (chlorine free) radical Ignore formula. 1

(ii) M1 Cl• + O3 ClO• + O2

M2 ClO• + O3 Cl• + 2O2 M1 and M2 could be in either order. Credit the dot anywhere on the radical. Penalise absence of dot once only. Individual multiples acceptable but both need to be doubled if two marks are to be awarded. 2 [7]

3.(a) (i) Initiation Br2 2Br•

First propagation Br• + CHF3 •CF3 + HBr

Second propagation Br2 + •CF3 CBrF3 + Br•

Termination

2•CF3 C2F6 OR CF3CF3 OR 2Br• Br2 OR Br• + •CF3 CBrF3 Penalise absence of dot once only Credit the dot anywhere on the radical 4

(ii) Ultra-violet / uv / sunlight OR T > 100°C OR high temperature 1

(b) (i) Page 76 Seven Kings High School

Displayed formula required with the radical dot on carbon 1

(ii) (The) C‒Br (bond) breaks more readily / is weaker than (the) C‒Cl (bond) (or converse) OR The C‒Br bond enthalpy / bond strength is less than that for C‒Cl (or converse) Requires a comparison between the two bonds Give credit for an answer that suggests that the UV frequency / energy may favour C‒Br bond breakage rather than C‒Cl bond breakage Ignore correct references either to size, polarity or electronegativity Credit correct answers that refer to, for example “the bond between carbon and bromine requires less energy to break than the bond between carbon and chlorine” 1

(iii) M1 Br• + O3 BrO• + O2

M2 BrO• + O3 Br• + 2O2 M1 and M2 could be in either order Credit the dot anywhere on the radical Penalise absence of dot once only Penalise the use of multiples once only

M3 One of the following They / it / the bromine (atom) • does not appear in the overall equation • is regenerated • is unchanged at the end • has not been used up • provides an alternative route / mechanism 3 [10]

M24.(a) (i) M1 Elimination M1 Credit “base elimination” but no other prefix. Page 77 Seven Kings High School

Penalise M2 if covalent KOH Penalise M4 for formal charge on C or Br of C−Br or incorrect partial charges on C−Br

M2 must show an arrow from the lone pair on the oxygen of a negatively charged hydroxide ion to a correct H atom Ignore other partial charges

M3 must show an arrow from a correct C−H bond adjacent to the C−Br bond to a correct C-C bond. Only award if an arrow is shown attacking the H atom of a correct adjacent C−H bond in M2 Penalise once only in any part of the mechanism for a line and two dots to show a bond

M4 is independent provided it is from their original molecule, BUT CE=0 for the mechanism (penalise M2, M3 and M4 only) if nucleophilic substitution mechanism is shown Maximum any 2 of 3 marks for the mechanism for wrong organic reactant or wrong organic product (if shown). Credit the correct use of “sticks” for the molecule except for the C−H being attacked

Award full marks for an E1 mechanism in which M4 is on the correct carbocation Penalise M4, if an additional arrow is drawn from Br eg to K+

NB These are double-headed arrows 4

(ii) Displayed formula for 3-methylbut-1-ene

All bonds and atoms must be drawn out, but ignore bond angles 1

(iii) Position(al) (isomerism or isomer) Penalise any other words that are written in addition to Page 78 Seven Kings High School these. 1

(b) (i) Displayed formula for 3-methylbutan-2-ol

All bonds and atoms must be drawn out, but ignore bond angles. 1

(ii) Any one from

• Lower / decreased temperature OR cold

• Less concentrated (comparative) OR dilute KOH

• Water (as a solvent) / (aqueous conditions) Ignore “pressure”. 1

(iii) Nucleophilic substitution Both words needed - credit phonetic spelling. 1

(iv) (Strong / broad) absorption / peak in the range 3230 to 3550 cm−1 or specified value in this range or marked correctly on spectrum Allow the words “dip” OR “spike” OR “trough” OR “low transmittance” as alternatives for absorption. 1 [10]

5.(a) (i) M1 Initiation

Cl2 2Cl• Penalise absence of dot once only.

M2 First propagation

Cl• + CHF3 CF3• +HCl Page 79 Seven Kings High School Penalise + or − charges every time.

M3 Second propagation

Cl2 + CF3• CClF3 + Cl•

Credit CF3• with the radical dot above / below / to either side.

M4 Termination (must make C2F6)

2 CF3• C2F6 or CF3CF3 Mark independently. 4

(ii) ultra-violet / uv / sun light

OR (very) high temperature

OR 500 °C ≤ T ≤ 1000 °C

OR 773 K ≤ T ≤ 1273 K 1

(b) (i) Cl• OR chlorine atom / chlorine (free−) radical / Cl (atom) Not ‘chlorine’ alone. Credit ‘Cl’ alone on this occasion. 1

(ii) 2O3 3O2 Or multiples. Ignore state symbols. If the correct answer is on the line OR clearly identified below some working, then ignore any working. 1 [7]

M26.(a) Electrophilic substitution Both words needed Ignore minor misspellings 1

(b) (i) Sn / HCl OR H2 / Ni OR H2 / Pt OR Fe / HCl OR Zn / HCl OR SnCl2 / HCl Ignore conc or dil with HCl, Page 80 Seven Kings High School

Allow (dil) H2SO4 but not conc H2SO4 + Not allow HNO3 or H Ignore NaOH after Sn / HCl Ignore catalyst 1

(ii) CH3C6H4NO2 + 6[H] → CH3C6H4NH2 + 2H2O

Allow molecular formulae as structures given

C7H7NO2 + 6[H] → C7H9N + 2H2O

Qu states use [H], so penalised 3H2 1

(iii) making dyes

OR making quaternary ammonium salts

OR making (cationic) surfactants

OR making hair conditioner

OR making fabric softener

OR making detergents 1

(c)

NO Mark for name of mechanism Allow SN1 M1 for lone pair on N and arrow to C or mid point of space between N and C M2 for arrow from bond to Br M3 for structure of protonated secondary amine Page 81 Seven Kings High School M4 for arrow from bond to N or + on N + − For M4: ignore RNH2 or NH3 removing H but penalise Br 4

(d) lone or electron pair on N If no mention of lone pair CE = 0 If lone pair mentioned but not on N then lose M1 and mark on

M1 1

in J spread / delocalised into ring (or not delocalised in K) Ignore negative inductive effect of benzene Allow interacts with Π cloud for M2

M2 1

less available (for protonation or donation in J)

in K there is a positive inductive effect / electron releasing)

more available (for protonation or donation in K)

M3 1 [11]

M27.D [1]

M28.C [1]

Page 82 Seven Kings High School M29.(a) M1 NaOH Only score M2 if M1 gained, but mark on from hydroxide. Mention of acid loses M1 & M2 1

M2 Aqueous/(warm) Ignore alcoholic / conc / dil. 1

M3 (Fractional) distillation or described Not just evaporation; not reflux Allow chromatography 1

(b) M1 S is CH3CH(CN)CH2CH3 Allow without brackets 1

Step 3

M2 KCN (mark on from CN-) Not HCN, not KCN with acid 1

M3 Alcoholic / (aqueous) Allow ethanolic Can only score M3 if M2 gained 1

Step 4

M4 H2

LiAlH4

Na Can only score M5 if M4 gained 1

M5 Ni or Pt or Pd

Ethoxyethane or ether

LiAlH4 with acid loses both M4 and M5

Ignore ‘followed by acid’

Ethanol

NOT NaBH4 OR Sn/HCl Penalise other extras as list Ignore pressure or temperature 1 [8]

Page 83 Seven Kings High School

M30.D [1]

M31.(a) NaOH/KOH IGNORE OH- NOT M1 if any mention of acidified/H+ in reagents or conditions 1

Reaction 1 = ethanolic/alcoholic AND reaction 2 = aqueous IGNORE temp NOT ethanoic 1

rxn 1 = base/proton acceptor 1

rxn 2 = nucleophile/lone pair donor/electron pair donor 1

(Base) Elimination NOT nucleophilic 1

M6 must show an arrow from the lone pair on the oxygen of a negatively charged hydroxide ion to a correct H atom

M7 must show an arrow from a correct C–H bond on C adjacent to the C of the C–Br bond to a correct C–C bond. Only award if an arrow is shown attacking the H atom of a correct adjacent C–H bond in M6

M8 is independent provided it is from their original molecule and shows curly arrow from C-Br to Br ALLOW correct E1 mechanism IGNORE incorrect inorganic products If forming pent-2-ene can award M8 only even if arrows in mechanism correct If C chain length or halogen wrong in reactant or product max 2/3 1 1 1

Page 84 Seven Kings High School

(b) 1

1 If no M2 and M3 ALLOW 1 mark if both structures OR both names correct NOT cis and trans

No free rotation around C=C ALLOW no rotation of C=C 1

2 different atoms/groups on each of the C=C Cs owtte IGNORE ‘functional’ 1

(c) Same volume/amount of AgNO3(aq) added to same volume/amount/no. of drops of haloalkane (in beaker/flask) in each experiment Both volume references needed IGNORE inappropriate volumes 1

Same temp OR same [AgNO3] each time 1

record time to measure sensible observation about the amount of AgCl ppt e.g. first appearance of ppt / ppt obscures mark / reading on a colorimeter IGNORE colour of ppt ALLOW silver mirror NOT reference to same time if describing method based on timing how long (for ppt to form) ALLOW gravimetric method based on same time Page 85 Seven Kings High School for each experiment 1

Rate = amount/time OR proportional to 1/time OR reference to shorter time = higher rate/longer time = lower rate ALLOW greater mass = higher rate if gravimetric method 1 [17]

M32.(a) UV light 1

CCl4 CCl3• + •Cl 1

(b) Cl• + O3 ClO• + O2 1

ClO• + O3 Cl• + 2O2 1

Moles freon = 1.78 × 10–4 × 103 / 104.5 = 1.70 × 10–3 1

Number of molecules = 1.70 × 10–3 × 6.02 × 1023 = 1.02 × 1021 1

Molecules in 500 cm3 = (1.02 × 1021 × 500 × 10–6) / 100 = 5.10 × 1015 Allow answer in the range 5.10–5.13 × 1015 Answer must be given to this precision 1 [7]

M33.(a) M1 ●Cl + O3 → ●ClO + O2 1

Page 86 Seven Kings High School

M2 ●ClO + O3 → ●Cl + 2O2 1 M1 and M2 could be in either order Credit the dot anywhere on the radical Penalise absence of dot once only Individual multiples acceptable but both need to be doubled if two marks are to be awarded Ignore state symbols

(b) Must be displayed formula 1

(c) Does not contain Cl or does not release Cl (atoms/radicals) or no C-Cl bonds or C-F bond(s) strong / does not break / no F (atom/radicals) released 1

(d) M1 CHF2CH3 + ●F → ●CF2CH3 + HF 1

M2 ●CF2CH3 + F2 → CF3CH3 + ●F 1 M1 and M2 could be in either order Credit the dot anywhere on the radical Penalise absence of dot once only

(e) M1 moles CF3CH3 = 1410/84(.0) (=16.8, 16.79 mol) 1

M2 molecules = M1 × 6.022 × 1023 = 1.01 × 1025 (3sf only) 1 Correct answer scores both marks Allow M2 for M1 × Avogadro with answer to 3 sf (but must have attempted to calculate moles for M1) Ignore incorrect units

Page 87 Seven Kings High School (f) (bonds) vibrate/stretch/bend OR (as bonds) are polar NOT polar molecules; ‘they’ = bonds 1 [9]

M34.(a) (i) CH3Cl + 2Cl2 → CHCl3 + 2HCl IGNORE state symbols ALLOW multiples 1 (ii) (Free-)radical substitution This answer only 1 (iii) Initiation:

Cl2 → 2Cl• Penalise absence of dot once only 1

1st Propagation step

Cl• + CH2Cl2 → •CHCl2 + HCl Penalise + and/or – charges every time 1

2nd Propagation step

•CHCl2 + Cl2 → CHCl3 + Cl•

ALLOW • anywhere on •CHCl2 but, if drawn out as a structure, then • must be on C 1

Termination

2 •CHCl2 → C2H2Cl4 Mark independently

ALLOW •CH2Cl + •CCl3 → C2H2Cl4 IGNORE state symbols throughout 1

(b) (i) CClF3 → •CF3 +Cl•

ALLOW • anywhere on •CF3 unless displayed 1

(ii) Cl• + O3 → ClO• + O2 Equations can be in either order Penalise absence of • once only 1

ClO• + O3 → 2O2 + Cl• ALLOW • anywhere on •ClO

NOT •O3 1 [9] Page 88 Seven Kings High School

M35.B [1]

M36.D [1]

Page 89 Seven Kings High School

Haloalkanes 2 Name: ______Class: ______

Date: ______

Time: 138 minutes

Marks: 138 marks

Comments:

Page 1 Seven Kings High School

Q1. (a) Propene reacts with hydrogen bromide by an electrophilic addition mechanism forming 2-bromopropane as the major product.

The equation for this reaction is shown below.

(i) Outline the mechanism for this reaction, showing the structure of the intermediate carbocation formed.

(ii) Give the structure of the alternative carbocation which could be formed in the reaction between propene and hydrogen bromide.

(5)

(b) A substitution reaction occurs when 2-bromopropane reacts with aqueous sodium hydroxide.

(i) Draw the structure of the organic product of this reaction and give its name.

Page 2 Seven Kings High School Structure

Name ......

(ii) Name and outline the mechanism for this reaction.

Name of mechanism ......

Mechanism

(5)

(i) Name the mechanism for this reaction.

......

(ii) State the role of sodium hydroxide in this reaction.

...... (2)

Page 3 Seven Kings High School (Total 12 marks)

Q2.Which one of the following is not a suitable method for the preparation of ethanol?

A oxidation of ethane

B hydration of ethene

C reduction of ethanal

D hydrolysis of bromoethane (Total 1 mark)

Q3.Which one of the following reactions involves nucleophilic addition?

A CH3CH = CH2 + HBr → CH3CHBrCH3

B CH3CH2CH3 + Cl2 → CH3CHClCH3 + HCl

C CH3CH2CH2Br + NaOH → CH3CH2CH2OH + NaBr

D CH3CH2CHO + HCN → CH3CH2CH(OH)CN (Total 1 mark)

Q4.Which one of the following mechanisms is not involved in the reaction sequence below?

CH3CH3 → CH3CH2Cl → CH3CH2OH → CH2=CH2 → CH3CH2Br

A electrophilic addition

B electrophilic substitution

C nucleophilic substitution

D free-radical substitution (Total 1 mark)

Page 4 Seven Kings High School Q5.Which one of the following can react both by nucleophilic addition and by nucleophilic substitution?

D (Total 1 mark)

Q6.In which one of the following are the curly arrows not used correctly?

D (Total 1 mark)

Q7.In which of the following is a curly arrow used incorrectly?

Page 5 Seven Kings High School

D (Total 1 mark)

Q8. Reaction of 2-bromobutane with potassium hydroxide can produce two types of product depending on the solvent used. In aqueous solution, the formation of an alcohol, E, is more likely but in ethanolic solution the formation of alkenes is more likely.

(a) For each type of product, name the type of reaction occurring and state the role of the potassium hydroxide. (4)

(b) Name alcohol E and draw its structural formula. By reference to the structure of the halogenoalkane, explain why the initial step in the mechanism of the reaction producing the alcohol occurs. (5)

(c) When 2-bromobutane reacts with ethanolic potassium hydroxide, two structurally isomeric alkenes are produced, one of which shows stereoisomerism.

Outline the mechanism for the formation of one of the structurally isomeric alkenes. Explain why two structurally isomeric alkenes are formed and draw the structure of the second structural isomer. Draw the structural formulae of the two stereoisomers. (8) (Total 17 marks)

Page 6 Seven Kings High School

Q9. (a) The equation below shows the reaction of 2-bromopropane with an excess of ammonia.

CH3CHBrCH3 + 2NH3 → CH3CH(NH2)CH3 + NH4Br

Name and outline the mechanism involved.

Name of mechanism …......

Mechanism

(5)

(b) When 2-bromopropane is heated with ethanolic potassium hydroxide, an elimination reaction occurs. State the role of potassium hydroxide and outline a mechanism for this reaction.

Role of potassium hydroxide ......

Mechanism

Page 7 Seven Kings High School

(5) (Total 10 marks)

Q10.Which one of the following reactions does not involve donation of an electron pair?

+ A H + CH3NH2 → CH3NH

− B AlCl3 + Cl → A1C1

− − C CH3Cl + CN → CH3CN + Cl

− − D Cl2 + I → Cl + I2 (Total 1 mark)

Q11.Which one of the following types of reaction mechanism is not involved in the above sequence?

CH3CH2CH3 (CH3)2CHCl (CH3)2CHCN

(CH3)2CHCH2NHCOCH3 (CH3)2CHCH2NH2

A free-radical substitution

B nucleophilic substitution

C elimination

D nucleophilic addition-elimination (Total 1 mark)

Q12. Ethene is an important starting point for the manufacture of plastics and

Page 8 Seven Kings High School pharmaceutical chemicals. Most of the ethene used by industry is produced by the thermal cracking of ethane obtained from North Sea gas (Reaction 1). It is also possible to make ethene either from chloroethane (Reaction 2) or from ethanol (Reaction 3).

(a) Give essential conditions and reagents for each of Reactions 2 and 3. (4)

(b) Name and outline a mechanism for Reaction 2. Suggest a reason why chloroethane is not chosen by industry as a starting material to make ethene commercially. (5)

(c) Name and outline a mechanism for Reaction 3. Suggest why this route to ethene may become used more commonly in the future as supplies of North Sea gas begin to run out. (6) (Total 15 marks)

Q13. The conversion of compound A into compound B can be achieved in two steps as shown below.

The intermediate compound, X, has an absorption at 1650 cm–1 in its infra-red spectrum.

(a) Identify compound X. Explain your answer. (2)

(b) For each step in this conversion, give the reagents and essential conditions required

Page 9 Seven Kings High School and outline a mechanism. (11)

(c) Show how the number of peaks in their proton n.m.r. spectra would enable you to distinguish between compounds A and B. (2) (Total 15 marks)

Q14.For this question refer to the reaction scheme below.

Which one of the following reagents would not bring about the reaction indicated?

A Step 1 : alcoholic KOH

B Step 2 : aqueous Br2

C Step 3 : aqueous NaOH

C Step 4 : concentrated H2SO4 (Total 1 mark)

Q15. (a) Chloromethane can be made by the reaction of chlorine with methane.

(i) Give one essential condition for this reaction.

......

(ii) Name the mechanism for this reaction.

Page 10 Seven Kings High School ......

(iii) Further substitution can occur during this reaction. Identify the main organic product when a large excess of chlorine is used in this reaction.

...... (3)

(b) Ethanenitrile can be made by reacting chloromethane with potassium cyanide.

(i) Write an equation for this reaction.

......

(ii) Name the mechanism for this reaction.

......

(iii) Explain, in terms of bond enthalpies, why bromomethane reacts faster than chloromethane with potassium cyanide.

......

...... (3)

(c) Ethanenitrile can be hydrolysed to a carboxylic acid by heating it under reflux with a dilute acid. Identify the carboxylic acid formed in this reaction.

...... (1)

(d) Chloromethane can react with ammonia to produce a primary amine.

(i) What feature of the chloromethane molecule makes it susceptible to attack by an ammonia molecule?

Page 11 Seven Kings High School ......

(ii) Name the amine produced in this reaction.

......

(iii) Outline a mechanism for this reaction.

(6) (Total 13 marks)

Q16. (a) Compounds with double bonds between carbon atoms can exhibit geometrical isomerism.

(i) Draw structures for the two geometrical isomers of 1,2-dichloroethene.

Isomer 1 Isomer 2

Page 12 Seven Kings High School

(ii) What feature of the double bond prevents isomer 1 from changing into isomer 2?

...... (3)

(b) When 2-chloropropane reacts with sodium hydroxide, two different reactions occur. Each reaction produces a different organic product.

(i) Outline a mechanism for Reaction 1 and state the role of the hydroxide ion in this reaction.

Mechanism

Role of the hydroxide ion ......

(ii) Outline a mechanism for Reaction 2 and state the role of the hydroxide ion in this reaction.

Mechanism

Page 13 Seven Kings High School Role of the hydroxide ion ...... (7) (Total 10 marks)

Q17.For this question refer to the reaction scheme below.

Which one of the following statements is not correct?

A Reaction of W with sodium cyanide followed by hydrolysis of the resulting product gives propanoic acid.

B Mild oxidation of Z produces a compound that reacts with Tollens’ reagent, forming a silver mirror.

C Z reacts with ethanoic acid to produce the ester propyl ethanoate.

C W undergoes addition polymerisation to form poly(propene). (Total 1 mark)

Q18. (a) Complete the mechanism below by drawing appropriate curly arrows.

(3)

Page 14 Seven Kings High School (b) Draw and name the geometrical E-Z isomers of pent-2-ene.

Isomer 1 Isomer 2

Name ...... …...... Name ...... …...... (2)

(i) Outline the mechanism for this reaction.

(ii) Identify the minor product formed in this reaction.

......

(iii) Explain why 2-bromopentane is the major product of this reaction.

......

...... (7) (Total 12 marks)

Page 15 Seven Kings High School

Q19. (a) Bromomethane, CH3Br, can be formed by a reaction between bromine and methane.

The mechanism for this reaction is similar to the mechanism for the chlorination of methane.

(i) Name the mechanism for this reaction.

......

(ii) Give the name of, and state an essential condition for, the first step in the mechanism for this reaction.

Name ......

Essential condition ......

(iii) Write an equation for a termination step in the mechanism for this reaction which gives ethane as a product.

......

(iv) Bromomethane can undergo further substitution. Write an overall equation for the reaction between bromomethane and bromine in which dibromomethane is formed.

Page 16 Seven Kings High School ...... (5)

(b) Bromomethane reacts with the nucleophile ammonia according to the following equation.

CH3Br + 2NH3 → CH3NH2 + NH4Br

(i) Explain what is meant by the term nucleophile.

......

(ii) Name the organic product of this reaction.

......

(iii) Outline a mechanism for this reaction.

(6) (Total 11 marks)

Q20. Consider the following reaction scheme.

Page 17 Seven Kings High School

(a) (i) Name the mechanism for Reaction 1.

......

(ii) Explain why 1-bromopropane is only a minor product in Reaction 1.

......

...... (3)

(b) Give a suitable reagent and state the essential conditions required for Reaction 3.

Reagent ......

Conditions ...... (2)

(c) The reagent used for Reaction 3 can also be used to convert 2-bromopropane into propene. State the different conditions needed for this reaction.

...... (1)

(d) Reaction 2 proceeds in two stages.

Stage 1 CH3CH=CH2 + H2SO4 → CH3CH(OSO2OH)CH3

Stage 2 CH3CH(OSO2OH)CH3 + H2O → CH3CH(OH)CH3 + H2SO4

Page 18 Seven Kings High School (i) Name the class of alcohols to which propan-2-ol belongs.

......

(ii) Outline a mechanism for Stage 1 of Reaction 2, using concentrated sulphuric acid.

(iii) State the overall role of the sulphuric acid in Reaction 2.

...... (6) (Total 12 marks)

Q21.How many different alkenes are formed when 2-bromo-2-methylbutane reacts with ethanolic potassium hydroxide?

A 2

B 3

C 4

Page 19 Seven Kings High School D 5 (Total 1 mark)

Page 20 Seven Kings High School

M1. (a) (i)

(ii) credit secondary carbocation here if primary carbocation has been used in (i) Ignore attack on this carbocation by 5

(b) (i) Structure:

No credit for propan-1-ol even when named correctly Credit propane-2-ol

Name: propan-2-ol (1) Not 2-hydroxypropane

(ii) Name of mechanism: nucleophilic substitution (1) (both words) (NOT SN1 orSN2)

Mechanism:

Page 21 Seven Kings High School

penalise incorrect polarity on C‑Br (M1) Credit the arrows even if incorrect haloalkane

If SN1, both marks possible

(ii) base (1) OR proton acceptor NOT nucleophile (base) 2 [12]

M2.A [1]

M3.D [1]

M4.B [1]

M5.B

Page 22 Seven Kings High School [1]

M6.D [1]

M7.C [1]

M8. (a) Alcohol: Reaction = Substitution (/ hydrolysis) (1) Ignore reference to nucleophilic, but electrophilic give zero

Alcohol: Role = nucleophile (/ lone pair donor) (1)

Alkene: reaction = elimination (1) Ignore ref to nucleophilic or electrophilic

Alkene: base (/ proton acceptor) (1) If no indication of order in (a) assume as in question. If order is wrong can still score 'role' mark. 4

(b) Alcohol: Role = butan-2-ol (1) Not 2-hydroxybutane or but-2-ol

Appropriate structure for CH3CH(OH) CH2CH3 (1) Brackets not essential

SN2 version SN1 version

– bond is polar C–Br bond is polar (1)

Lone pair of OH– C–Br bond breaks (1)

Attacks the Cδ+ forming carbocation / carbonium ion (1)

M1 can be scored from a diagram, M2 and M3 from written explanation only 5

Page 23 Seven Kings High School (c)

If but-2-ene not given here it may be obtained from cis / trans isomer

H lost from different carbon atoms (1) H removes from C1 and C3 to give two isomers (1) Draws clear Cis and trans isomers for but-2-ene Can score these marks from a diagram

8 [17]

M9. (a) Name of mechanism: nucleophilic substitution (1) Mechanism:

Marks SN1 using same points M2 requires

Page 24 Seven Kings High School 5

(b) Role of potassium hydroxide: Base (1) Mechanism:

5 [10]

M10.D [1]

M11.C [1]

M12. (a) Reaction 2: NaOH OR KOH (1) M1 alcohol (ic) OR ethanol (ic)(1) M2 ignore heat Condition mark linked to correct reagent but award M2 if OH– or base or alkali mentioned

Reaction 3: concentrated H2SO4 OR H3PO4 M1 (1) heat (1) M2 OR 150°C - 200°C Condition mark linked to correct reagent but award M2 if

H2SO4 or H3PO4, but not concentrated

Penalise reagent and condition if dilute H2SO4 / H3PO4 4

Page 25 Seven Kings High School

(b) Mechanism:

Award M3 independently M1 and M2 must be to / from correct places

E1 mechanism possible in which M2

Name: of mechanism = elimination (1) NOT dehydrohalogenation Ignore “base” OR “nucleophilic” before elimination

Reason: Reaction 2 has (very) low yield (1) 5 QoL OR chloroethane has to be made (from ethane) OR chloroethane is expensive OR chloroethane is not redily available

Name of mechanism = elimination (1) NOT dehydration alone

Reason: Ethanol could come from (fermentation of) renewable

Page 26 Seven Kings High School QoL sugars / glucose / carbohydrates / sources (1) 6 [15]

M13. (a) Identity of X; 2-methylpropene (1) Absorption at 1650 cm–1 indicates an alkene present (1)

OR a chemical answer e.g. Br2 (aq) brown to colourless 2

(b) Reagents Step 1 KOH (allow NaOH) (1) alcoholic (1) warm (1) Only allow solvent and warm if reagent correct

Step 2 HBr (1)

Mechanism: A → X

Or a carbocation mechanism

Mechanism X → B

(c) A gives three peaks (1) B gives one peak (1) Allow one for “A has more peaks than B” when no number of peaks is given 2 [15]

Page 27 Seven Kings High School

M14.B [1]

M15. (a) (i) UV light OR sunlight OR T 450°C (1) NOT high T

(ii) (free) radical substitution (1)

(iii) CCl4 (1) OR named 3

(b) (i) CH3Cl + KCN → CH3CN + KCl (1) CN– Cl–

(ii) nucleophilic substitution (1)

(iii) C–Br bond is weaker (than C–Cl bond) OR C–Br bond enthalpy is less than C–Cl (1) Ignore electronegativity 3

(d) (i) OR C–Cl is polar (1) OR C atom is electron deficient / δ+

(ii) methylamine (1) only

(iii) SN1 scores full marks

Page 28 Seven Kings High School

6 [13]

M16. (a) (i)

(ii) restricted rotation OR no rotation OR cannot rotate (1) 3

(b) (i) Mechanism:

Page 29 Seven Kings High School M1 and M2 independent Curly arrows must be from a bond or a lone pair Do not penalise sticks Penalise M1 if precedes (penalise this once) Penalise incorrect δ+ δ– for M2 Penalise + on C atom for M2 Only allow M1 for incorrect haloalkane

Role of the hydroxide ion: nucleophile (1) electron pair donor lone pair donor NOT nucleophilic substitution

(ii) Mechanism:

Only allow M1 and M2 for incorrect haloalkane unless RE on (i) + charge on H on molecule, penalise M1 M3 independent M2 must be to correct C–C M1 must be correct H atom Credit M1 and M2 via carbocation mechanism

No marks after any attack of C by OH–

Role of the hydroxide ion: base (1) proton acceptor accepts H+ 7 [10]

Page 30 Seven Kings High School

M17.A [1]

M18. (a) M1 curly arrow from lone pair on oxygen of hydroxide ion to H atom on C-H adjacent to C-Br 1

M2 curly arrow from single bond of adjacent C-H to adjacent single bond C-C (only credit M2 if M1 is being attempted to correct H atom) 1

M3 curly arrow from C-Br bond to side of Br atom (credit M3 independently) 1

(b) Ml credit a correct structure for either geometrical E-Z isomer and its designation as either cis or trans. OR credit two correct geometrical E-Z isomer structures (ignore the names) OR credit two correct names for cis pent-2-ene and trans pent-2-ene (ignore the structures) 1

M2 credit a second mark if all four parts of the required structures and names are correct. (credit “linear” structures) (insist on the alkyl groups being attached clearly by C-C bonds) 1

(c) (i) Ml curly arrow from middle of C = C bond to H atom on H-Br (penalise M1 if partial negative charge or formal positive charge on H) (penalise Ml if pent-2-ene is used) 1

M2 curly arrow from H-Br bond to side of Br atom 1

M3 correct structure for correct secondary carbocation 1

M4 curly arrow from lone pair on bromide ion to the positive carbon of carbocation, ensuring that bromide ion has a negative charge.

Page 31 Seven Kings High School (with the exception of pent-2-ene, if the wrong alkene is used, only penalise the structure M3) (penalise the use of two dots in addition to a covalent bond, once only) 1

(ii) 1-bromopentane 1

(iii) Ml 2-bromopentane is formed via the secondary (or 2°) carbocation 1

OR 1-bromopentane is formed via the primary (or 1°) carbocation M2 a secondary carbocation is more stable than a primary carbocation - award this mark only if the quality of language justifies the award. (the argument must involve clear statements about carbocations) 1 [12]

M19. (a) (i) (Free) radical substitution (Both words needed) 1

(ii) M1 initiation ONLY 1

M2 ultra-violet light OR sunlight OR 1000°C T 450 °C (Ignore reference to temperature if included with uv light) (Penalise “high temperature” for M2) 1

(iii) → C2H6

(OR CH3CH3 as alternative to C2H6) 1

(iv) CH3Br + Br2 → CH2Br2 + HBr 1

Page 32 Seven Kings High School

(b) (i) Electron pair donor OR species with an electron pair able to form a covalent bond. 1

(ii) Methylamine (Credit “aminomethane”) 1

(iii)

M1 arrow to show breakage of C – Br bond 1

M2 arrow from lone pair on N of NH3 to form bond with C 1

M4 arrow from bond of N – H to N atom of CH3 3 (Ignore partial charges on haloalkane but penalise if incorrect)

(Accept for M3) (Full credit for carbocation mechanism; M1 for C – Br bond breakage and M2 for lone pair attack on carbocation) (Second mole of ammonia not essential to mechanism for full credit) 1 [11]

M20. (a) (i) Electrophilic addition (Both words required) 1

(ii) M1 the reaction to form 1-bromopropane goes via the primary

Page 33 Seven Kings High School carbocation OR 1o carbocation

OR via

M2 primary carbocations are less stable than secondary carbocations (Credit converse arguments for M1 and M2 i.e. the reaction to form 2-bromopropane goes via the secondary carbocation , M1, and secondary carbocations are more stable than primary carbocations, M2) (Accept the use of “carbonium ions” as an alternative to carbocation) 1

(b) M1 NaOH OR KOH OR correct name 1

M2 aqueous or solution in water (ignore heat, reflux etc.) (Penalise M1 for hydroxide ion alone, but mark on and credit M2)

(Credit M2 ONLY for H2O as reagent and heat / warm / T=50 to 100oC) (NaOH(aq) scores M1 and M2 provided it is not contradicted) (Penalise M2 if NaOH(aq) followed by concentrated or ethanol) (Penalise M1 and M2 if followed by acid) 1

(c) Ethanolic OR alcoholic OR CH3CH2OH / CH3OH solvent OR aqueous ethanol/alcohol OR higher temperature (must be comparative) (Ignore heat or heat under reflux) (Credit part (c) independently from part (b)) (Penalise “ethanoic”) 1

(d) (i) Secondary OR 2o 1

(ii)

M1 arrow from double bond to H of H – O bond M2 arrow from bond to oxygen atom to show H – O bond breakage M4 arrow from lone pair of electrons to carbon atom of carbocation

(Penalise M1 if arrow goes to H2SO4 or to formal positive charge on H, but ignore partial charges on sulphuric acid unless wrong) Page 34 Seven Kings High School (Credit M2 for H+ ion) (For M4, accept negative charge anywhere on the ion) 4

(iii) Catalyst ONLY (Ignore homogeneous, heterogeneous) 1 [12]

M21.A [1]

Page 35

Name: ______Kinetics exam pack

Class: ______

Date: ______

Time: 265 minutes

Marks: 234 marks

Comments:

Page 1 of 76 Q1. An equation for the equilibrium reaction between hydrogen, iodine and hydrogen iodide is shown below.

H2(g) + I2(g) 2HI(g)

(a) The curve in the diagram below illustrates the reaction profile for this equilibrium reaction without a catalyst.

(i) Draw on the diagram a curve to illustrate the reaction profile for this equilibrium reaction with a catalyst. (2)

(ii) Use the diagram to deduce whether the formation of hydrogen iodide from hydrogen and iodine is exothermic or endothermic.

______(1)

(iii) State what the diagram suggests about the sum of the bond enthalpies for the reactant molecules compared with the product molecules.

______

______(1)

(iv) In terms of p and q, identify the following for this equilibrium without a catalyst.

A value for the activation energy for the forward reaction ______

A value for the overall enthalpy change for the forward reaction

______(2)

(b) A mixture of H2(g) and I2(g) was allowed to reach equilibrium.

(i) State the effect of a catalyst on the rate of attainment of this equilibrium.

Page 2 of 76 ______(1)

(ii) State and explain the effect of an increase in total pressure on the rate of attainment of this equilibrium.

Effect of an increase in pressure on rate ______

Explanation ______

______

______(3) (Total 10 marks)

Q2. Group 2 metals and their compounds are used commercially in a variety of processes and applications.

(a) State a use of magnesium hydroxide in medicine.

______(1)

(b) Calcium carbonate is an insoluble solid that can be used in a reaction to lower the acidity of the water in a lake.

Explain why the rate of this reaction decreases when the temperature of the water in the lake falls.

______

______(3)

(i) Explain why strontium has a higher melting point than barium.

______

Page 3 of 76 (2)

(ii) Write an equation for the reaction of strontium with water.

______(1)

(d) Magnesium can be used in the extraction of titanium.

(i) Write an equation for the reaction of magnesium with titanium(IV) chloride.

______(1)

(ii) The excess of magnesium used in this extraction can be removed by reacting it with dilute sulfuric acid to form magnesium sulfate.

Use your knowledge of Group 2 sulfates to explain why the magnesium sulfate formed is easy to separate from the titanium.

______

______(1) (Total 9 marks)

Q3. Nitric acid is manufactured from ammonia in a process that involves several stages.

(a) In the first stage, ammonia is converted into nitrogen monoxide and the following equilibrium is established.

–1 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) ∆H = –905 kJ mol

The catalyst for this equilibrium reaction is a platinum–rhodium alloy in the form of a gauze. This catalyst gauze is heated initially but then remains hot during the reaction.

(i) In terms of redox, state what happens to the ammonia in the forward reaction.

______(1)

(ii) Suggest a reason why the catalyst must be hot.

______(1)

(iii) Suggest a reason why the catalyst remains hot during the reaction.

______(1)

Page 4 of 76 (iv) State how a catalyst increases the rate of a reaction.

______

______(2)

(b) In the second stage, nitrogen monoxide is converted into nitrogen dioxide. The equation for the equilibrium that is established is shown below.

–1 2NO(g) + O2(g) 2NO2(g) ∆H = –113 kJ mol

Explain why the equilibrium mixture is cooled during this stage of the process.

______

______(2)

+ – 2NO2(g) + H2O(l) → H (aq) + NO3 (aq) + HNO2(aq)

Give the oxidation state of nitrogen in each of the following.

NO2 ______

– NO3 ______

HNO2 ______(3) (Total 10 marks)

Q4. The diagram shows the Maxwell–Boltzmann distribution for a sample of gas at a fixed temperature. Ea is the activation energy for the decomposition of this gas.

Page 5 of 76

Energy Ea

Emp is the most probable value for the energy of the molecules.

(a) On the appropriate axis of this diagram, mark the value of Emp for this distribution.

On this diagram, sketch a new distribution for the same sample of gas at a lower temperature. (3)

(b) With reference to the Maxwell–Boltzmann distribution, explain why a decrease in temperature decreases the rate of decomposition of this gas.

______

______(2) (Total 5 marks)

Q5. An equation for the decomposition of hydrogen peroxide is shown below.

2H2O2 2H2O + O2

State the measurements you would take in order to investigate the rate of this reaction.

Page 6 of 76 ______

______

______(Total 2 marks)

Q6. A student calculated that a value for the enthalpy change of neutralisation is –51.2 kJ mol–1.

The design of a possible hand-warmer using hydrochloric acid and sodium hydroxide was discussed. It was proposed that 500 cm3 of hydrochloric acid should be used in a flexible, sealed plastic container with a breakable tube of solid sodium hydroxide also in the container. On breaking the tube, the sodium hydroxide would be released, react with the acid and produce heat. A 40 °C temperature rise was thought to be suitable.

(a) Calculate the heat energy, in J, required to raise the temperature of the reaction mixture by 40 °C. Assume that the reaction mixture has a density of 1.00 g cm–3 and a specific heat capacity of 4.18 J K–1 g–1. Assume that all of the heat energy given out is used to heat the reaction mixture.

______

______(2)

(b) Use your answer from part (a) and the value for the enthalpy change of neutralisation of –51.2 kJ mol–1 to calculate the minimum amount, in moles, and hence the minimum mass of sodium hydroxide required in the breakable tube. (If you could not complete the calculation in part (a) assume that the heat energy required was 77 400 J. This is not the correct answer).

Show your working.

Moles of NaOH ______

______

Mass of NaOH ______

______(3)

(c) Use the amount, in moles, of sodium hydroxide from part (b) to calculate the minimum concentration, in mol dm–3, of hydrochloric acid required in the 500 cm3 of solution used in the sealed container.

______

Page 7 of 76 ______

______(1)

(d) Suggest one possible risk to a person who uses a hand-warmer containing sodium hydroxide and hydrochloric acid.

______

______(1)

(e) A commercial hand-warmer uses powdered iron sealed in a plastic container. A valve allows air to enter the container, and oxygen in the air reacts slowly with the iron to form solid iron(lll) oxide. The heat released warms the container.

(i) Write an equation for this reaction between iron and oxygen to form iron(lll) oxide.

______(1)

(ii) One version of an iron-oxygen hand-warmer advertises that it is designed to stay warm for up to four hours. Other than by increasing the amount of iron in the container, state one change to the iron in the hand-warmer that would increase this time. Explain why this change to the iron might not be an advantage.

Change to the iron ______

______

Explanation ______

______

______(3)

(f) Another type of hand-warmer uses sodium thiosulfate. Sodium thiosulfate is very soluble in water at 80 °C but is much less soluble at room temperature. When a hot, concentrated solution of sodium thiosulfate is cooled it does not immediately crystallise. The sodium thiosulfate stays dissolved as a stable ’super-saturated’ solution until crystallisation is triggered. Heat energy is then released when the sodium thiosulfate crystallises.

(i) This type of hand-warmer is re-usable. Suggest one environmental advantage that a sodium thiosulfate hand-warmer has over the other two types.

______(1)

(ii) Describe the two steps that you would take to make the sodium thiosulfate hand-warmer ready for re-use.

Step 1 ______

Page 8 of 76 ______

Step 2 ______

______(2) (Total 14 marks)

Q7. The diagram below shows a Maxwell–Boltzmann distribution for a sample of gas at a fixed temperature. Ea is the activation energy for the decomposition of this gas.

(a) (i) On this diagram, sketch the distribution for the same sample of gas at a higher temperature. (2)

(ii) With reference to the Maxwell–Boltzmann distribution, explain why an increase in temperature increases the rate of a chemical reaction.

______

______(2)

(b) Dinitrogen oxide (N2O) is used as a rocket fuel. The data in the table below show how the activation energy for the decomposition of dinitrogen oxide differs with different catalysts.

2N2O(g) 2N2(g) + O2(g)

Ea / kJ mol–1

Without a catalyst 245

With a gold catalyst 121

Page 9 of 76 With an iron catalyst 116

With a platinum catalyst 136

(i) Use the data in the table to deduce which is the most effective catalyst for this decomposition.

______(1)

(ii) Explain how a catalyst increases the rate of a reaction.

______

______(2) (Total 7 marks)

Q8. The rate of a chemical reaction is influenced by the size of the activation energy. Catalysts are used to increase the rates of chemical reactions but are not used up in the reactions.

(a) Give the meaning of the term activation energy.

______

______(2)

(b) Explain how a catalyst increases the rate of a reaction.

______

______(2)

(c) The diagram below shows the Maxwell–Boltzmann distribution of molecular energies, at a constant temperature, in a gas at the start of a reaction. On this diagram the most probable molecular energy at this temperature is shown by the symbol Emp The activation energy is shown by the symbol Ea

Page 10 of 76

To answer the questions (c)(i) to (c)(iv), you should use the words increases, decreases or stays the same. You may use each of these answers once, more than once or not at all.

(i) State how, if at all, the value of the most probable energy (Emp) changes as the total number of molecules is increased at constant temperature.

______(1)

(ii) State how, if at all, the number of molecules with the most probable energy (Emp) changes as the temperature is decreased without changing the total number of molecules.

______(1)

(iii) State how, if at all, the number of molecules with energy greater than the activation energy (Ea) changes as the temperature is increased without c hanging the total number of molecules.

______(1)

(iv) State how, if at all, the area under the molecular energy distribution curve changes as a catalyst is introduced without changing the temperature or the total number of molecules.

______(1)

(d) For each of the following reactions, identify a catalyst and name the organic product of the reaction.

(i) The fermentation of an aqueous solution of glucose.

Catalyst ______

Name of organic product ______

______(2)

Page 11 of 76 (ii) The hydration of but-2-ene.

Catalyst ______

Name of organic product ______

______(2) (Total 12 marks)

Q9. The diagram shows the Maxwell-Boltzmann distribution of molecular energies in a gas at two different temperatures.

(a) One of the axes is labelled. Complete the diagram by labelling the other axis. (1)

(b) State the effect, if any, of a solid catalyst on the shape of either of these distributions.

______

______(1)

(c) In the box, write the letter, V, W, X or Y, that represents the most probable energy of the molecules at the lower temperature.

(1)

(d) Explain what must happen for a reaction to occur between molecules of two different gases.

______

Page 12 of 76 ______(2)

(e) Explain why a small increase in temperature has a large effect on the initial rate of a reaction.

______

______(1) (Total 6 marks)

Q10. (a) Figure 1 shows the volume of hydrogen gas collected when a sample of magnesium reacted with an excess of dilute hydrochloric acid.

The rate of this reaction can be studied by measuring the time it takes for a given volume of hydrogen to be collected.

Figure 1

Time / s

(i) State the meaning of the term rate of reaction.

______

______(1)

(ii) State and explain what has happened to the rate of this reaction at point W in Figure 1.

Page 13 of 76 ______

______

______(2)

(iii) In terms of collision theory explain why, at a fixed temperature, the rate of this reaction doubles when the concentration of the hydrochloric acid doubles.

______

______(2)

(b) In a study of the reaction in part (a), a student referred to activation energy.

(i) State the meaning of the term activation energy.

______

______(1)

(ii) Complete Figure 2 by drawing the shape of the reaction profile from reactants to products for an exothermic reaction. Show the position of the products. Show and label the activation energy.

Figure 2

Page 14 of 76 (2)

(i) Write an equation for the reaction of barium with water.

______(1)

(ii) A solution containing barium ions can be used to show the presence of sulfate ions in an aqueous solution of sodium sulfate.

Write the simplest ionic equation for the reaction that occurs and state what is observed.

Simplest ionic equation

______

Observation

______(2)

(iii) State one use of barium sulfate in medicine. Explain why this use is possible, given that solutions containing barium ions are poisonous.

Use ______

______

Explanation ______

______

______(2) (Total 13 marks)

Q11. A study of equilibrium is important for understanding chemical reactions.

(a) State le Chatelier’s principle.

______

(Extra space) ______

______

Page 15 of 76 (1)

(b) Catalysts play an important role in many reactions.

(i) State the meaning of the term catalyst. Explain, in general terms, how catalysts work.

Meaning of the term catalyst ______

______

How catalysts work ______

______

______(3)

(Extra space) ______

______

(ii) State the effect, if any, of a catalyst on the time taken to reach equilibrium.

______(1)

(iii) State the effect, if any, of a catalyst on the position of an equilibrium.

______(1)

ΔHᶿ / kJ mol−1

P H2(g) + l2(g) 2Hl(g) −10

Q CO2(g) + 3H2(g) CH3OH(g) + H2O(g) −49

R N2O4(g) 2NO2(g) +58

S N2(g) + 3H2(g) 2NH3(g) −92

T C2H4(g) + H2O(g) CH3CH2OH(g) −42

In each of parts (c)(i) to (c)(v), you should record in the box one of the letters, P, Q, R, S or T, that corresponds to the equilibrium that best fits the information provided. You may use each letter once, more than once or not at all.

(i) A decrease in temperature at constant pressure shifts the position of this equilibrium from right to left.

Page 16 of 76

(1)

(ii) This equilibrium uses concentrated phosphoric acid as a catalyst in a hydration reaction.

(1)

(iii) A decrease in pressure at constant temperature shifts the position of this equilibrium from left to right.

(1)

(iv) There is no change in the position of this equilibrium when the pressure is increased at constant temperature.

(1)

(v) An increase in the concentration of steam at constant temperature and constant pressure shifts the position of this equilibrium from right to left.

(1) (Total 11 marks)

Q12. A student carried out an experiment to determine the rate of decomposition of hydrogen peroxide into water and oxygen gas. The student used 100 cm3 of a 1.0 mol dm–3 solution of hydrogen peroxide at 298 K and measured the volume of oxygen collected. Curve R, in each of Figures 1, 2 and 3, shows how the total volume of oxygen collected changed with time under these conditions.

(a) Draw a curve on Figure 1 to show how the total volume of oxygen collected will change with time if the experiment is repeated at 298 K using 100 cm3 of a 2.0 mol dm–3 solution of hydrogen peroxide.

Figure 1

Page 17 of 76

(2)

(b) Draw a curve on Figure 2 to show how the total volume of oxygen collected will change with time if the experiment is repeated at 298 K using 100 cm 3 of a 0.4 mol dm–3 solution of hydrogen peroxide.

Figure 2

(2)

(c) Draw a curve on Figure 3 to show how the total volume of oxygen collected will change with time if the original experiment is repeated at a temperature higher than 298 K. You should assume that the gas is collected at a temperature of 298 K.

Figure 3

Page 18 of 76

(2)

(d) Explain why the slope (gradient) of curve R decreases as time increases.

______

(Extra space) ______

______

(e) The student discovered that hydrogen peroxide decomposes at a faster rate when a few drops of aqueous hydrogen bromide are added to the solution. The student found on the Internet that this decomposition is thought to proceed in two steps as shown by the following equations.

Step 1 H2O2 + HBr HBrO + H2O

Step 2 HBrO + H2O2 H2O + O2 + HBr

(i) Write an equation for the overall reaction.

______(1)

(ii) Give one reason, other than the increase in rate of reaction, why the student was able to deduce that hydrogen bromide behaves as a catalyst in this two-step reaction.

______

______(1)

Page 19 of 76 Q13. When iodine molecules are dissolved in aqueous solutions containing iodide ions, they – react to form triiodide ions (I3 ).

– – I2 + I I3

2– The rate of the oxidation of iodide ions to iodine by peroxodisulfate(VI) ions (S2O8 ) was – studied by measuring the concentration of the l3 ions at different times, starting at time = 0, – when the reactants were mixed together. The concentration of the l3 ions was determined by measuring the absorption of light using a spectrometer.

The table below shows the results.

– –3 Time / Concentration of l3 / mol dm s

10 0.23

20 0.34

30 0.39

40 0.42

50 0.47

60 0.44

70 0.45

– (a) Plot the values of the concentration of I3 (y-axis) against time on the grid below.

Page 20 of 76

(2)

(b) A graph of these results should include an additional point. On the grid, draw a ring around this additional point. (1)

Page 21 of 76 (d) Draw a tangent to your curve at time = 30 seconds. Calculate the slope (gradient) of this tangent and hence the rate of reaction at 30 seconds. Include units with your final answer. Show your working.

______

______(4) (Total 9 marks)

Q14. (a) In an investigation of the rate of reaction between hydrochloric acid and pure magnesium, a student obtained the following curve.

The reaction of magnesium with dilute hydrochloric acid is exothermic.

Use your understanding of collision theory to explain why the student did not obtain a straight line.

______

______(3)

(b) The magnesium used in a laboratory experiment was supplied as a ribbon. The ribbon was stored in an open plastic bag exposed to the air.

Page 22 of 76 Explain why it is important to clean the surface of this magnesium ribbon when investigating the rate of its reaction with hydrochloric acid.

______

______(2)

(c) Magnesium ribbon reacts with hot water. Heated magnesium ribbon reacts with steam. State two differences between these reactions.

Difference 1 ______

______

Difference 2 ______

______(2)

Use your knowledge of the solubilities of Group 2 sulfates to explain why these reactions of magnesium and calcium with dilute sulfuric acid are so different.

______

______(3) (Total 10 marks)

Q15. The apparatus in the figure below was set up to measure the time taken for 20.0 cm3 of sodium thiosulfate solution to react with 5.0 cm3 of hydrochloric acid in a 100 cm3 conical flask at 20 °C. The timer was started when the sodium thiosulfate solution was added to the acid in the flask. The timer was stopped when it was no longer possible to see the cross on the paper.

Page 23 of 76

What is likely to decrease the accuracy of the experiment?

A Rinsing the flask with acid before each new experiment.

B Stirring the solution throughout each experiment.

C Using the same piece of paper for each experiment.

D Using different measuring cylinders to measure the volumes of acid and sodium thiosulfate.

(Total 1 mark)

Q16. An equation for the decomposition of hydrogen peroxide is

2H2O2 2H2O + O2

(a) The rate of reaction can be determined by collecting the oxygen formed and measuring its volume at regular intervals.

Draw a diagram to show the apparatus that you would use to collect and measure the volume of the oxygen formed.

(2)

(b) Explain how you could use your results from the experiment in part (a) to determine

Page 24 of 76 the initial rate of this reaction.

______

______(2)

Outline the essential features of an additional experiment to show that the rate of decomposition is increased by the addition of cobalt(II) chloride. Use the same method and the same apparatus as in part (a).

______

______(2) (Total 6 marks)

Q17. Methanol, for use as a fuel, can be produced by the reaction of carbon monoxide with hydrogen.

–1 CO(g) + 2H2(g) CH3OH(g) ΔH = –90 kJ mol

7 The reaction is typically carried out at ⇌300 °C and 3 × 10 Pa, in the presence of a catalyst. (a) The graph shows the Maxwell–Boltzmann distribution for a mixture of carbon monoxide and hydrogen at 300 °C.

Page 25 of 76 (i) Sketch a second curve on the graph to show the distribution of molecular energies in this mixture at a higher temperature. (1)

(ii) Explain with reference to both curves on the graph how a small change in temperature leads to a large change in the rate of reaction.

______

______(2)

(b) Both the rate of production and equilibrium yield of methanol are considered when choosing the most appropriate conditions for the operation of this process on an industrial scale.

(i) State and explain the effect of a higher pressure on the equilibrium yield of methanol.

______

______(3)

(ii) By considering both rate and yield, state why the reaction is carried out at a temperature of 300 °C rather than at a higher temperature.

______

______(2) (Total 8 marks)

Q18. The carboxylic acid 3-methylbutanoic acid is used to make esters for perfumes. The following scheme shows some of the reactions in the manufacture of this carboxylic acid.

Page 26 of 76

(a) One of the steps in the mechanism for Reaction 1 involves the replacement of the functional group by bromine.

(i) Use your knowledge of organic reaction mechanisms to complete the mechanism for this step by drawing two curly arrows on the following equation.

(2)

(ii) Deduce the name of the mechanism in part (i).

Give the IUPAC name of (CH3)2CHCH2Br

______

______(2)

(b) Reaction 3 is an acid-catalysed reaction in which water is used to break chemical bonds when the CN functional group is converted into the COOH functional group. Infrared spectroscopy can be used to distinguish between the compounds in this reaction.

Deduce the name of the type of reaction that occurs in Reaction 3.

Identify one bond in (CH3)2CHCH2CN and a different bond in (CH3)2CHCH2COOH that can be used with infrared spectroscopy to distinguish between each compound. For each of these bonds, give the range of wavenumbers at which the bond absorbs. Use Table A on the Data Sheet when answering this question.

______

Page 27 of 76 ______

______

______(3)

(c) When 3-methylbutanoic acid reacts with ethanol in the presence of an acid catalyst, an equilibrium is established. The organic product is a pleasant-smelling ester.

(CH3)2CHCH2COOH + CH3CH2OH (CH3)2CHCH2COOCH2CH3 + H2O an ester

The carboxylic acid is very expensive and ethanol is inexpensive. In the manufacture of this ester, the mole ratio of carboxylic acid to ethanol used is 1 to 10 rather than 1 to 1.

(i) Use Le Chatelier’s principle to explain why a 1 to 10 mole ratio is used. In your explanation, you should not refer to cost.

______

(Extra space) ______

______(3)

(ii) Explain how a catalyst increases the rate of a reaction.

______

(Extra space) ______

______(2) (Total 12 marks)

Q19. The following figure shows the Maxwell.Boltzmann distribution of molecular energies in a

Page 28 of 76 sample of gas at temperature T.

(a) One of the axes is labelled. Label the other axis. (1)

(b) State why the curve starts at the origin.

______

______(1)

(c) Which of the following, A, B or C, describes what the value of Y represents in the figure? Write the correct letter, A, B or C, in the box.

A The energy needed for a successful collision B The minimum energy needed for a reaction to occur C The most probable energy

(1)

(d) On the figure above, draw a distribution of molecular energies in this sample of gas at a higher temperature. (2)

(e) The pressure of the original sample of gas is doubled at temperature T.

State the effect, if any, of this change on the value of Y.

______

______(1) (Total 6 marks)

Page 29 of 76 Q20. A student investigated how the initial rate of reaction between sulfuric acid and magnesium at 20 °C is affected by the concentration of the acid.

The equation for the reaction is

H2SO4(aq) + Mg(s) MgSO4(aq) + H2(g)

(a) The student made measurements every 20 seconds for 5 minutes. The student then repeated the experiment using double the concentration of sulfuric acid.

State a measurement that the student should make every 20 seconds. Identify the apparatus that the student could use to make this measurement.

______

______(2)

(b) State one condition, other than temperature and pressure, that would need to be kept constant in this investigation.

______

______(1)

(i) Draw a diagram to show how the student could separate the magnesium hydroxide from the reaction mixture.

(2)

(ii) Suggest one method the student could use for removing soluble impurities from the sample of magnesium hydroxide that has been separated.

______

Page 30 of 76 ______

______

______(1) (Total 6 marks)

Q21. A dynamic equilibrium is established when gas A is mixed with gas B at a given temperature.

A(g) + B(g) C(g) + D(g)

The figure below shows how the concentrations of reactants and products change with time.

(a) (i) On the appropriate axis of the figure, place an X to show the time when equilibrium is first established. (1)

(ii) State how the rate of the forward reaction and the rate of the reverse reaction are related to each other at equilibrium.

______

______(1)

(b) Give the meaning of the term dynamic in the context of a dynamic equilibrium.

______

______(1)

(i) State and explain the effect, if any, of this change on the position of this equilibrium.

Page 31 of 76 Effect ______

Explanation ______

______

______(2)

(ii) State and explain the effect, if any, of this change on the time taken to reach this equilibrium.

Effect ______

Explanation ______

______

______(3) (Total 8 marks)

Q22. Calamine lotion can contain a mixture of zinc carbonate and zinc oxide in suspension in water. A manufacturer of calamine lotion claims that a sample contains 15.00 g of zinc carbonate and 5.00 g of zinc oxide made up to 100 cm3 with distilled water.

(a) A chemist wanted to check the manufacturer’s claim. The chemist took a 20.0 cm3 sample of the calamine lotion and added it to an excess of sulfuric acid. The volume of carbon dioxide evolved was measured over time. The chemist’s results are shown in the table.

Time / s 0 15 30 45 60 75 90 105 120 135

Volume / cm3 0 135 270 380 470 530 560 570 570 570

(i) Plot a graph of the results in the table on the grid. The volume should be on the y-axis. Draw a best-fit curve through all the points.

Page 32 of 76

(3)

(ii) Estimate the time taken for the reaction to be completed.

______

Page 33 of 76 (1)

(b) (i) The volume of carbon dioxide in part (a) was measured at 293 K and at a pressure of 100 kPa.

Use information from your graph to calculate the maximum amount, in moles, of carbon dioxide evolved from the zinc carbonate in this 20.0 cm3 sample.

The gas constant, R = 8.31 J K−1 mol−1

Show your working.

______

______(3)

(ii) Use your answer to part (i) to calculate the mass of zinc carbonate in the 20.0 cm3 sample of calamine lotion.

(If you were unable to complete part (i), you may assume that the amount of carbon dioxide evolved was 0.0225 mol. This is not the correct answer.)

______

______(2)

(iii) Calculate the difference between your answer to part (ii) and the manufacturer’s claim that there are 15.00 g of zinc carbonate in 100 cm3 of the calamine lotion.

Express this difference as a percentage of the manufacturer’s claim.

(If you were unable to complete part (ii), you may assume that the mass of zinc carbonate in the 20 cm3 sample of calamine lotion was 2.87 g. This is not the correct answer.)

Difference ______

Percentage ______

______(2)

Page 34 of 76 part (a). Include in your diagram a method for collecting and measuring the carbon dioxide. The apparatus should be airtight. (2) (Total 13 marks)

Q23. Hydrogen is produced in industry from methane and steam in a two-stage process.

(a) In the first stage, carbon monoxide and hydrogen are formed. The equation for this reaction is

−1 CH4(g) + H2O(g) CO(g) + 3H2(g) ΔH = +206 kJ mol

(i) Use Le Chatelier’s principle to state whether a high or low temperature should be used to obtain the highest possible equilibrium yield of hydrogen from this first stage. Explain your answer.

Temperature ______

Explanation ______

______

______(3)

(ii) Le Chatelier’s principle suggests that a high pressure will produce a low yield of hydrogen in this first stage.

Explain, in terms of the behaviour of particles, why a high operating pressure is used in industry.

______

______(2)

(iii) A nickel catalyst is used in the first stage.

Explain why the catalyst is more effective when coated onto an unreactive

Page 35 of 76 honeycomb.

______

______(2)

(b) The second stage is carried out in a separate reactor. Carbon monoxide is converted into carbon dioxide and more hydrogen is formed.

The equation for this reaction is

−1 CO(g) + H2O(g) CO2(g) + H2(g) ΔH = −41 kJ mol

Use Le Chatelier’s principle to state the effect, if any, of a decrease in the total pressure on the yield of hydrogen in this second stage. Explain your answer.

Effect ______

Explanation ______

______

______(2) (Total 9 marks)

Q24. This question involves the use of kinetic data to deduce the order of a reaction and calculate a value for a rate constant.

The data in Table 1 were obtained in a series of experiments on the rate of the reaction between compounds A and B at a constant temperature.

Table 1

Experiment Initial Initial Initial rate concentration of A concentration of B / mol dm−3 s−1 / mol dm−3 / mol dm−3

1 0.12 0.26 2.10 × 10−4

2 0.36 0.26 1.89 × 10−3

3 0.72 0.13 3.78 × 10−3

Page 36 of 76 (a) Show how these data can be used to deduce the rate expression for the reaction between A and B.

______

______(3)

The data in Table 2 were obtained in two experiments on the rate of the reaction between compounds C and D at a constant temperature.

Table 2

Experiment Initial Initial Initial rate concentration of C concentration of D / mol dm−3 s−1 / mol dm−3 / mol dm−3

4 1.9 × 10−2 3.5 × 10−2 7.2 × 10−4

5 3.6 × 10−2 5.4 × 10−2 To be calculated

The rate equation for this reaction is

rate = k[C]2[D]

(b) Use the data from experiment 4 to calculate a value for the rate constant, k, at this temperature. Deduce the units of k.

k = ______Units = ______(3)

Page 37 of 76 (c) Calculate a value for the initial rate in experiment 5.

Initial rate = ______mol dm−3 s−1 (1)

(d) The rate equation for a reaction is

rate = k[E]

Explain qualitatively why doubling the temperature has a much greater effect on the rate of the reaction than doubling the concentration of E.

______

______(3)

(e) A slow reaction has a rate constant k = 6.51 × 10−3 mol−1 dm3 at 300 K.

−1 Use the equation ln k = ln A – Ea / RT to calculate a value, in kJ mol , for the activation energy of this reaction.

The constant A = 2.57 × 1010 mol−1 dm3. The gas constant R = 8.31 J K−1 mol−1.

Activation energy = ______(2) (Total 12 marks)

Page 38 of 76 Q25. The graph below shows a typical energy distribution for particles of an ideal gas in a sealed container at a fixed temperature.

Which of the following statements is true?

A Position A represents the mean energy of a molecule in the container.

B Addition of a catalyst moves the position of EA to the right.

C The area under the curve to the right of EA represents the number of molecules with enough energy to react.

D The position of the peak of the curve at a higher temperature is further away from both axes. (Total 1 mark)

Q26. When an aqueous solution of ethanoic acid reacts with magnesium, the progress of reaction can be followed using the equipment shown in Figure 1 to measure the volume of hydrogen produced.

Figure 1

Figure 2 shows how the volume of hydrogen produced varies with time when 396 mg of

Page 39 of 76 magnesium are added to 30.0 cm3 of 0.600 mol dm−3 ethanoic acid.

Figure 2

(a) The equation for the reaction between ethanoic acid and magnesium is shown.

2CH3COOH(aq) + Mg(s) → (CH3COO)2Mg(aq) + H2(g)

With the aid of calculations, show that the magnesium is in excess in this reaction.

______

______(3)

(b) The reaction was repeated using 20 cm3 of 0.800 mol dm−3 of ethanoic acid solution with all other conditions the same. The magnesium was still in excess.

Sketch a line on Figure 2 to show how the volume of hydrogen produced varies with

Page 40 of 76 time in this second experiment.

Space for working.

(2) (Total 5 marks)

Q27. The graph shows the Maxwell−Boltzmann distribution of molecular energies in a sample of gas at a fixed temperature.

(a) Label the horizontal axis on the graph. (1)

(b) On the graph, sketch a distribution of molecular energies for this sample of gas at a higher temperature. (2)

Explain why an increase in temperature increases the rate at which this gas decomposes.

______

Page 41 of 76 ______

______

______(2) (Total 5 marks)

Q28. The experiment was repeated at 20 °C using a 250 cm3 conical flask.

Which statement is correct about the time taken for the cross to disappear when using the larger conical flask?

A The time taken will not be affected by using the larger conical flask.

B The time taken will be decreased by using the larger conical flask.

C The time taken will be increased by using the larger conical flask.

D It is impossible to predict how the time taken will be affected by using the larger conical flask.

(Total 1 mark)

Q29. This question is about the Maxwell–Boltzmann distribution of molecular energies in a sample of a gas shown in the figure below.

Which letter best represents the mean energy of the molecules?

Page 42 of 76 C

D (Total 1 mark)

Q30. This question is about the Maxwell–Boltzmann distribution of molecular energies in a sample of a gas shown in the following figure.

What does the area under the curve represent?

A The total energy of the particles.

B The total number of particles.

C The number of particles that can react with each other.

D The total number of particles that have activation energy. (Total 1 mark)

Q31. The question below is about the Maxwell–Boltzmann distribution shown for a sample of a gas, X, at two different temperatures.

Page 43 of 76

Which statement is correct for the higher temperature?

The area under the curve to the left of Ea A decreases.

B The total area under the curve increases.

C The activation energy decreases.

D More molecules have the mean energy. (Total 1 mark)

Q32. The question below is about the Maxwell–Boltzmann distribution shown for a sample of a gas, X, at two different temperatures.

Page 44 of 76

Which letter shows the mean energy of the molecules at the higher temperature?

A P

B Q

C R

D S (Total 1 mark)

Q33. Line X in the diagram represents the volume (V) of gas formed with time (t) in a reaction between an excess of magnesium and aqueous sulfuric acid.

Which line represents the volume of hydrogen formed, at the same temperature and pressure, when the concentration of sulfuric acid has been halved?

Page 45 of 76 A

(Total 1 mark)

Q34. The diagram shows the Maxwell−Boltzmann distribution of molecular energies in a gas at two different temperatures.

Page 46 of 76

Which letter represents the most probable energy of the molecules at the higher temperature?

D (Total 1 mark)

Q35. Nitryl chloride reacts with nitrogen monoxide according to the equation:

ClNO2(g) + NO (g) NO2(g) + ClNO(g)

The Maxwell–Boltzmann distribution curve in⟶ Figure 1 shows the distribution of molecular energies in 1 mol of this gaseous reaction mixture (sample 1) at 320 K.

Page 47 of 76 (a) On the same axes, draw a curve for sample 1 at a lower temperature. (2)

(b) Explain the effect that lowering the temperature would have on the rate of reaction.

______

______(2)

(c) A Maxwell–Boltzmann distribution curve was drawn for a second sample of the reaction mixture in the same reaction vessel. Figure 2 shows the results.

Deduce the change that was made to the reaction conditions.

Explain the effect that this change has on the rate of reaction.

Change ______

______

Explanation ______

______

Page 48 of 76 ______

______

______(3) (Total 7 marks)

Page 49 of 76 Mark schemes

Q1. (a) (i) M1 drawn curve starts at reactants and ends at products Tapered lines into the original curve gain credit for M1

M2 curve peak is below the one drawn in the question (and may show one/two humps) Mark M1 and M2 independently 2

(ii) Exothermic (reaction) Ignore “ΔH is negative” 1

(iii) Σ bond (enthalpy) reactants < Σ bond (enthalpy) products

The sum for H2 and I2/reactants is less than/lower than/smaller than the sum for 2HI/products OR The sum for 2HI/products is more than/larger than/bigger than the

sum for H2 and I2/reactants Accept “It OR the sum will be smaller or less” 1

(iv) M1 p 2

M2 – (q – p)

p – q

– q + p M2 demands that the sign for an exothermic reaction is part of the outcome mathematically. Ignore case

(b) (i) Increase/speed up/faster (rate of attainment of equilibrium)

Increase/speed up/faster rate of both forward and reverse reaction

Increase/speed up/faster rate of reaction Credit “It took less time” 1

(ii) M1 Increase/speed up/faster (rate of attainment of equilibrium)

M2 More particles/molecules in a given volume/space

Page 50 of 76 OR the particles/molecules are closer together OR an increase in concentration.

M3 More/higher chance of successful/effective/productive collisions (between particles) OR more collisions/higher chance of collisions (of particles) with E>EAct If M1 is blank, mark on and credit M1 in the text If M1 is given as “decrease”/“no effect”/”no change” then CE = 0 for clip In M1, if increase both the forward and reverse reaction, but no mention of rate, penalise M1 but mark on. In M1, if increase either forward rate or reverse rate only, then penalise M1 but mark on.

Penalise M3 if an increase in the value of EAct/energy of particles is stated. Max 1 for M2 and M3 if reference to “atoms” 3 [10]

Q2. (a) Antacid

to neutralise acidity

eases indigestion Credit suitable reference to indigestion or to laxative or to relief of constipation 1

(b) M1 Decrease in T decreases the energy of the particles/ions/H+/molecules

M3 Few(er)/Less effective/productive/successful collisions QoL 3

Correct reference to size of cations/proximity of electrons M1 (For Sr) delocalised electrons closer to cations/positive ions/atoms/nucleus

cations/positive ions/atoms are smaller

Page 51 of 76 cation/positive ion/atom or it has fewer (electron) shells/levels Ignore general Group 2 statements Penalise M1 if Sr or Ba is said to have more or less delocalised electrons Ignore reference to shielding CE = 0 for reference to molecules or intermolecular forces or covalent bonds

Relative strength of metallic bonding M2 (Sr) has stronger attraction between the cations/positive ions/ atoms/nucleus and the delocalised electrons

stronger metallic bonding (assume argument refers to Sr but accept converse argument for Ba) 2 Ignore “Van der Waals forces (between atoms)” but penalise if “between molecules”

(ii) Sr + 2H2O → Sr(OH)2 + H2 Or multiples 1

(d) 2Mg + TiCl4 → 2MgCl2 + Ti Or multiples 1 [9]

Q3. (a) (i) Oxidation

Oxidised ONLY 1

(ii) Any one from

• to provide/overcome activation energy

• to provide the minimum energy to make the reaction go/start NOT simply to increase the (initial) reaction rate. 1

(iii) The reaction is exothermic OR releases heat (energy) 1

(iv) M1 Catalysts provide an alternative route/pathway OR an alternative mechanism

(in this case) surface adsorption occurs (or a description of adsorption) Ignore reference to "surface" alone

Page 52 of 76 M2 Lowers the activation energy

of lower activation energy 2

(b) M1 The (forward) reaction is exothermic OR the (forward) reaction releases heat

The reverse reaction is endothermic or absorbs heat

M2 – Direction of change N.B. M2 depends on correct M1 At lower temperatures,

• the equilibrium yield of NO2 is greater

• more NO2 is formed

• equilibrium shifts (left) to right

• (equilibrium) favours the forward reaction

(OR converse for higher temperatures) 2

- NO3 (+) 5

HNO2 (+) 3 3 [10]

Q4. (a) M1 On the energy axis Emp at the maximum of the original peak

M1 The limits for the horizontal position of Emp are defined as above the word “the” in the sentence below the graph.

M2 The peak of their new curve is displaced to the left and higher than the original.

M3 All of the following are required

• The new curve starts at the origin and should begin to separate from the original almost immediately

• and the new curve crosses the original curve once

• and an attempt has been made to draw the new curve correctly towards the energy axis below the original curve but not to touch the original curve or the axis 3

Page 53 of 76 (b) The rate of reaction decreases as the temperature decreases because

M1 A decrease in the number / proportion of molecules with E ≥ Ea OR fewer molecules have E ≥ Ea OR fewer molecules have sufficient / enough energy to react / decompose In M1 Ignore “molecules have less energy”. Ignore “less energetic collisions”. Ignore “molecules do not gain activation energy”. Ignore “fewer collisions”. Credit “particles” for “molecules” but NOT “atoms”.

M2 Fewer effective / productive / successful collisions in a given time / given period OR fewer frequent effective / productive / successful collisions OR lower rate of effective / productive / successful collisions Ignore “chance of collision”; this alone does not gain M2 2 [5]

Q5. Measure volume of gas / mass loss If ‘measure concentration’ must explain how to score mark 1

At (regular) time intervals Ignore references to temperature Accept ‘against time’ Do not accept ‘with time’ or ‘over time’ on its own 1 [2]

Q6. (a) q = 500 × 4.18 × 40 Do not penalise precision. 1

= 83600 J Accept this answer only. Ignore conversion to 83.6 kJ if 83600 J shown. Unit not required but penalise if wrong unit given. Ignore the sign of the heat change. An answer of 83.6 with no working scores one mark only. An answer of 83600 with no working scores both marks. 1

(b) Moles (= 83.6 / 51.2) = 1.63 Using 77400 alternative gives 1.51 mol Allow (a) in kJ / 51.2 Do not penalise precision. 1

Mass = 1.63 × 40(.0) = 65.2 (g)

Page 54 of 76 Allow 65.3 (g) Using 77400 alternative gives 60.4 to 60.5 Allow consequential answer on M1.

1 mark for Mr (shown, not implied) and 1 for calculation. Do not penalise precision. 2

(d) Container splitting and releasing irritant / corrosive chemicals Must have reference to both aspects; splitting or leaking (can be implied such as contact with body / hands) and hazardous chemicals. Allow ‘burns skin / hands’ as covering both points Ignore any reference to ‘harmful’. Do not allow ‘toxic’. 1

(e) (i) 4Fe + 3O2 → 2Fe2O3 Allow fractions / multiples in equation. Ignore state symbols. 1

(ii) Iron powder particle size could be increased / surface area lessened Decrease in particle size, chemical error = 0 / 3 Change in oxygen, chemical error = 0 / 3 1

Not all the iron reacts / less reaction / not all energy released / slower release of energy / lower rate of reaction Mark points M2 and M3 independently. 1

Correct consequence of M2 An appropriate consequence, for example • too slow to warm the pouch effectively • lower temperature reached • waste of materials 1

(f) (i) Conserves resources / fewer disposal problems / less use of landfill / fewer waste products Must give a specific point. Do not allow ‘does not need to be thrown away’ without qualification. Do not accept ‘no waste’. 1

(ii) Heat to / or above 80 °C (to allow thiosulfate to redissolve) Accept ‘heat in boiling water’. If steps are transposed, max 1 mark.

Page 55 of 76 1

Allow to cool before using again Reference to crystallisation here loses this mark. 1 [14]

Q7. (a) (i) M1 The peak of the new curve is displaced to the right.

M2 All of the following are required

• The new curve starts at the origin

• The peak of the new curve is lower than the original

• and the new curve only crosses the original curve once

• and an attempt has been made to draw the new curve correctly towards the energy axis but not to touch the original curve

• the new curve must not start to diverge from the original curve M1 is low demand M2 is higher demand. 2

(ii) M1 Increase in the number/proportion of molecules with E ≥ Ea

OR more molecules have E ≥ Ea

OR more molecules have sufficient energy to react

M2 More effective/productive/successful collisions Ignore “molecules have more energy” Ignore “more energetic collisions” Ignore “molecules gain activation energy” Ignore “more collisions” Accept “particles” for “molecules” but NOT “atoms” Ignore “chance of collision”; this alone does not gain M2 2

(b) (i) Iron OR Fe 1

(ii) M1 Catalysts provide an alternative route/pathway/mechanism

(in this case) surface adsorption/surface reaction occurs. For M1, not simply “provides a surface” alone

M2 that has a lower activation energy

Page 56 of 76 lowers the activation energy For M2, the candidate may use a definition of activation energy without referring to the term 2 [7]

Q8. (a) M1 The activation energy is the minimum / least / lowest energy Mark independently Ignore “heat” and ignore “enthalpy”

M2 (energy) for a reaction to occur / to go / to start

OR (energy) for a successful / effective collision Ignore “breaking the bonds” 2

(b) M1 Catalysts provide an alternative route OR an alternative mechanism OR alternative / different path(way)

M2 Lowers the activation energy Mark independently Ignore reference to “surface” 2

(ii) Increases Credit “increase” or “increased” 1

(iii) Increases Credit “increase” or “increased” 1

(iv) Stay(s) the same 1

(d) (i) M1 yeast or zymase

M2 ethanol Ignore “enzyme” In M2, ignore “alcohol” and ignore any formula 2

(ii) M1 (Concentrated) H3PO4 OR (Concentrated) H2SO4

M2 butan-2-ol Credit correct names Ignore “hydrogenphosphate or hydrogensulfate” Ignore “dilute” or “aq” Do not penalise absence of hyphens in name. In M2, ignore any formula 2

Page 57 of 76 [12]

Q9. (a) Number / proportion / percentage / fraction of molecules Ignore “particles” 1

(b) None OR no effect OR no change 1

(d) Answers in either order

M1 collision OR collide Mark independently

M2 collision / molecules / particles Ignore “correct” amount of energy

with the activation energy

OR with E > Eact

OR with sufficient /enough energy

OR with the minimum energy

OR with the correct orientation 2

(e) A small increase in temperature results in many more / much higher proportion of / a lot more / significantly more molecules / particles / collisions with E ≥ Eact/ energy greater than the activation energy / sufficient energy / enough energy / minimum energy to react (compared with a small increase in concentration)

Not just “more molecules with E ≥ Eact” The answer must convey that the increase is significant Accept reference to “atoms”, “molecules”, “particles” Ignore “species” 1 [6]

Q10. (a) (i) Change in concentration (of a substance / reactant / product) in unit time / given time / per (specified) unit of time This may be written mathematically OR may refer to the gradient of a graph of concentration / volume against time

Amount of substance formed / used up in unit time / given time / per (specified) unit of time Ignore additional information including reference to collisions

Page 58 of 76 1

(ii) At W

M1 (QoL)

The rate / it is zero

The magnesium has all reacted / has been used up Ignore reference to the acid being used up

No more collisions possible between acid and Mg

Reaction is complete / it has stopped

No more hydrogen / product is produced 2

(iii) M1

Twice / double as many particles / hydrogen ions (in a given volume) Penalise reference to (hydrochloric acid) molecules in M1 Penalise reference to “HCl particles” in M1

Twice / double as much hydrochloric acid

Twice / double as many effective / successful collisions (in a given time)

Twice / double as many collisions with either sufficient energy to react OR with E ≥ Ea

double the successful / effective collision frequency 2

(b) (i) The activation energy is the minimum energy for a reaction to go / start

Minimum energy for a successful/ effective collision 1

(ii) M1 Products lower than reactants on the profile Mark independently

Page 59 of 76 M2 Activation energy (Ea) shown and labelled correctly from reactants to peak of curve Mark independently 2

Ba + 2H2O Ba2+ + 2OH− + H2 Allow multiples Ignore state symbols 1

(ii) M1 Ba2+ + SO42− BaSO4 Ignore state symbols in M1 Not multiples in M1

M2 White precipitate / solid Extra ions must be cancelled Penalise contradictory observations in M2 2

(iii) M1 Barium meal / barium swallow / barium enema Accept a correct reference to M1 written in the explanation in M2, unless contradictory

OR used in X-rays OR to block X-rays OR X-ray contrast medium OR CT scans

M2 BaSO4 / barium sulfate is insoluble (and therefore not toxic) For M2 NOT barium ions NOT barium NOT barium meal and NOT “It” Ignore radio-tracing 2 [13]

Q11. (a) (If any factor is changed which affects an equilibrium), the (position of) equilibrium will shift / move so as to oppose / counteract the change. Must refer to equilibrium Ignore reference to “system” alone A variety of wording will be seen here and the key part is the last phrase

(When a system / reaction in equilibrium is disturbed), the (position of) equilibrium shifts / moves in a direction which tends to reduce the disturbance An alternative to shift / move would be the idea of changing / altering the position of equilibrium 1

(b) (i) M1

Page 60 of 76 A substance that speeds up the reaction / alters the rate but is chemically unchanged at the end / not used up Both ideas needed for M1 Credit can score for M1, M2 and M3 from anywhere within the answer

M2 Catalysts provide an alternative route / alternative pathway / different mechanism

M3 that has a lower activation energy / Ea

OR lowers the activation energy / Ea 3

(ii) (Time is) less / shorter / decreases / reduces Credit “faster”, “speeds up”, “quicker” or words to this effect 1

(iii) None 1

(ii) T 1

(iii) R 1

(iv) P 1

(v) Q 1 [11]

Q12. (a) Award in either order for curve “Steeper” requires line to be on the left of the original line, starting from the origin

M1 curve is steeper than original and starts at the origin

M2 curve levels at the top line on the graph 2

(b) Award in either order for curve “Shallower” requires line to be on the right of the original line, starting from the origin

M1 curve is shallower than original and starts at the origin

M2 curve levels at the first line on the graph 2

Page 61 of 76 (c) M1 curve would be steeper than original “Steeper” requires line to be on the left of the original line, starting from the origin

M2 curve levels at the same original volume of O2 2

(d) M1 The (concentration / amount of) H2O2 or reactant falls / decreases / used up Mark independently

The number of H2O2 or reactant molecules/ particles falls / decreases

The rate of reaction / rate of decomposition / rate of formation of oxygen / frequency of collisions / (effective) collisions in a given time decreases / is slower 2

(e) (i) 2H2O2 → 2H2O + O2 Ignore state symbols Accept only this equation or its multiples Extra species must be crossed through 1

(ii) hydrogen bromide / it does not appear in the overall equation

hydrogen bromide / it is not used up in the reaction / unchanged at the end of the reaction

hydrogen bromide / it is regenerated / re-formed (in Step 2) 1 [10]

Q13. (a) Sensible scales Plotted points (including 0,0) must cover more than half the graph paper. If axis wrong way round lose this mark but mark on consequentially. Do not allow broken axis. 1

Plots points correctly 1

(b) Ring around the origin 1

Page 62 of 76 Line must pass within ± 1 small square of each plotted point except the anomaly (allow one plot ± 2 small square – at 40 or 60s). 1

Line through points is best fit and ignores anomaly (allow one plot ± 2 small square) Lose this mark if student’s line is doubled. Kinked line loses this mark. Lose this mark if the line does not pass through the origin + / – 1 small square. Lose this mark if the line deviates to anomaly. 1

(d) Draws suitable tangent Must touch the curve at 30s and must not cross the curve. Lose this mark if the tangent is unsuitable but mark on. 1

Chooses appropriate x and y values from their graph Mark consequentially if axes plotted the wrong way around. Allow information clearly shown on graph. 1

Correctly calculates y / x Difference in x values and y values must be at least 10 small squares in either direction. 1

Gives answer with correct units (mol dm–3 s–1) or correct variant Lose this mark if answer not to minimum of 2 significant figures and no units or incorrect units are given. If student has used axis the wrong way round, the unit mark can be awarded for either the correct unit based on their graph or for the correct unit for rate. 1 [9]

Q14. (a) As concentration increases the amount of heat given out increases / temperature increases (M1) Any order. Ignore references to an exothermic reaction. 1

More successful collisions or reactions in a given time OR more particles have the activation energy (M2) Allow could be a second / nth order reaction. 1

(An increase in temperature or more heat given out) increases the rate of a reaction (M3) 1

(b) The magnesium is coated with an oxide / MgO (M1)

Page 63 of 76 Allow magnesium hydroxide. 1

Slower with hot water or faster with steam

The hot water produces Mg(OH)2 / the hydroxide OR steam produces MgO / the oxide

(Slow) bubbling with hot water OR bright white light / flame / white solid with steam 2 max

(d) Magnesium sulfate is soluble and calcium sulfate is insoluble / slightly soluble / magnesium sulfate is more soluble / calcium sulfate is less soluble / correct trend in solubility (M1) Any order. M1 requires a comparison of the two solubilities.

Calcium sulfate coats the surface of the calcium (M2)

Coating prevents further contact with / reaction by the acid (M3) ‘Calcium sulfate forms a protective coating’ scores M2 only. 3 [10]

Q15. A [1]

Q16. (a) Stoppered flask or similar with side arm Allow gas outlet through stopper. 1

Calibrated container for collection eg gas syringe Allow collection over water, but must use calibrated vessel for collection. Lose 1 mark if apparatus is not gas tight. 1

(b) Plot a graph of ‘volume (of gas)’ against ‘time’ 1

Determine the slope (gradient) at the beginning 1

Page 64 of 76 (c) Repeat with same volume or concentration of hydrogen peroxide and at the same temperature Ignore references to results. Do not allow ‘keep everything the same’ or words to that effect. Must mention volume or concentration and temperature. 1

Add cobalt(II) chloride to one experiment 1 [6]

Q17. (a) (i) Curve drawn from origin with peak clearly lower and to right. New curve crosses original once only, finishes above original and does not clearly curve up IGNORE relative areas 1

(ii) (Relative areas under curves indicate) many (owtte) more molecules with E greater than or equal to Ea (at higher T) or reverse argument ALLOW ‘particles’ IGNORE ‘atoms’ 1 (Large) increase in (number of) successful (owtte) collisions per unit time OR ‘frequency of successful collisions’ 1

(b) (i) Yield increases Yield decreases/stays the same CE = 0 If not answered mark on 1 More moles/molecules (of gas) on left/fewer on right/3 on left 1 on right 1 Equilibrium shifts/moves (to right) to reduce pressure/oppose higher pressure No M3 if ‘more moles on right’ in M2 IGNORE ‘favours’ NOT just ‘oppose the change’ QoL means that M3 is only awarded if these ideas are clearly linked in one statement 1

(ii) Higher T would increase rate but decrease yield/make less methanol OR Lower T decreases rate but increases yield; If no mention of both rate AND (idea of) yield max 1 1 Chosen T is a compromise/balance (between rate and yield) owtte 1 [8]

Page 65 of 76 Q18. (a) (i) M1 double-headed curly arrow from the lone pair of the bromide ion to the C atom of the CH2 Penalise additional arrows.

M2 double-headed arrow from the bond to the O atom

As follows

(ii) M1 nucleophilic substitution M1 both words needed (allow phonetic spelling).

M2 1-bromo(-2-)methylpropane M2 Require correct spelling in the name but ignore any hyphens or commas. 2

(b) M1 hydrolysis For M1 give credit for ‘hydration’ on this occasion only.

M2 C≡N with absorption range 2220–2260 (cm−1) Credit 1 mark from M2 and M3 for identifying C≡N and either O–H(acids) or C=O or C–O without reference to wavenumbers or with incorrect wavenumbers.

M3 O–H(acids) with absorption range 2500–3000 (cm−1)

C=O with absorption range 1680–1750 (cm−1)

C–O with absorption range 1000–1300 (cm−1) Apply the list principle to M3 3

M2 (By Le Chatelierߣs principle) the position of equilibrium is driven / shifts / moves to the right / L to R / in the forward direction / to the product(s)

M3 – requires a correct statement in M2

(The position of equilibrium moves)

to oppose the increased concentration of ethanol

to oppose the increased moles of ethanol

Page 66 of 76 to lower the concentration of ethanol

to oppose the change and decrease the ethanol If no reference to M1, marks M2 and M3 can still score BUT if M1 is incorrect CE=0 If there is reference to ‘pressure’ award M1 ONLY. 3

(ii) M1

Catalysts provide an alternative route / pathway / mechanism

surface adsorption / surface reaction occurs For M1, not simply ‘provides a surface’ as the only statement. M1 may be scored by reference to a specific example.

that has a lower / reduced activation energy

lowers / reduces the activation energy Penalise M2 for reference to an increase in the energy of the molecules. For M2, the student may use a definition of activation energy without referring to the term. Reference to an increase in successful collisions in unit time alone is not sufficient for M2 since it does not explain why this has occurred. 2 [12]

Q19. (a) Amount / number / proportion / percentage / fraction / moles of molecules / particles Penalise an incorrect qualification of the number eg NOT number of molecules with E greater than Ea. Not ‘atoms’. 1

(b) There are no molecules / particles with zero energy

All of the molecules / particles are moving / have some energy Not ‘atoms’. The answer should relate the energy to the molecules. 1

(d) M1 The peak of the new curve is displaced to the right and lower than the original

Page 67 of 76 M2 All of the following needed

• The new curve starts at the origin and should begin to separate from the original almost immediately

• and the new curve only crosses the original curve once

• and the total area under the new curve is approximately the same as the original

• and an attempt has been made to draw the new curve correctly towards the axis above the original curve but not to touch the original curve 2

(e) None / no effect / stays the same 1 [6]

Q20. (a) (Measure the) volume of gas / mass of the container + contents 1

(b) Any one of:

• Mass of magnesium Allow amount of magnesium.

• Surface area of magnesium 1

Filter paper Must show filter paper as at least two sides of a triangle (V-shaped) for gravity filtration or horizontal filter paper for vacuum filtration. 1

(ii) Wash with / add (a small amount of cold) water Ignore filtering. 1 [6]

Page 68 of 76 Q21. (a) (i) Award mark for X on the time axis at the point where the lines just become horizontal Allow this mark if X is above the letters “sh” in the word “show” in part(ii) - in the range of lines 31 to 33. 1

(ii) They are equal / the same

Forward (rate) = Reverse / backward (rate) Allow the word ‘speed’ in this context. Ignore reference to concentration. 1

(b) Both OR forward and reverse reactions occur at the same time

OR both are occurring at once

OR both occur all of the time

OR both are ongoing

OR both never stop Ignore ‘at equal rates’. Ignore reference to concentration or equilibrium. The idea that both reactions occur simultaneously is essential. The simple idea of ‘both reactions occurring’ is insufficient for the mark. 1

M2 requires correct M1 In M2, ignore reference to particles or atoms.

M2 Equal (number of) moles / molecules on both sides 2

(ii) M1 Less time or it decreases or (equilibrium) reached faster (ie M1 is a reference to time taken) If M1 is ‘more time / it increases’ or ‘no effect’, then CE=0 for the clip. Reference to faster / increased rate / increased speed alone penalises M1, but mark on M2 and M3.

M2 More particles / molecules in a given volume / space

OR the particles / molecules are closer together If M1 is blank, then look for all three marks in the text.

M3 More successful / productive collisions in a given time

OR more collisions with E>EAct in a given time

Page 69 of 76 OR more frequent successful / productive collisions

OR increased / greater successful / productive collision frequency / rate Ignore reference to reactants / products.

Penalise M3 if an increase / decrease in the value of EAct is stated. 3 [8]

Q22. (a) (i) Uses sensible scales. Lose this mark if the plotted points do not cover half of the paper. Lose this mark if the graph plot goes off the squared paper Lose this mark if volume is plotted on the x-axis 1

All points plotted correctly Allow ± one small square. 1

Smooth curve from 0 seconds to at least 135 seconds − the line must pass through or close to all points (± one small square). Make some allowance for the difficulties of drawing a curve but do not allow very thick or doubled lines. 1

(ii) Any value in the range 91 to 105 s Allow a range of times within this but not if 90 quoted. 1

(b) (i) Using pV = nRT This mark can be gained in a correctly substituted equation. 1

100 000 × 570 × 10−6 = n × 8.31 × 293 Correct answer with no working scores one mark only. 1

n = 0.0234 mol Do not penalise precision of answer but must have a minimum of 2 significant figures. 1

(ii) Mol of ZnCO3 = 0.0234 Mark consequentially on Q6

M1 1

Mass of ZnCO3 = M1 × 125.4 = 2.9(3) or 2.9(4) g If 0.0225 used then mass = 2.8(2) g

M2 1

Page 70 of 76 (iii) Difference = (15.00 / 5) − Ans to b If 2.87 g used then percentage is 4.3

M1 1

Percentage = (M1 / 3.00) × 100 Ignore precision beyond 2 significant figures in the final answer If 2.82 g used from (ii) then percentage = 6.0

M2 1

Gas collection over water or in a syringe Collection vessel must be graduated by label or markings Ignore any numbered volume markings. 1 [13]

Q23. (a) (i) M1 High (temperature) OR Increase (the temperature) If M1 is incorrect CE = 0 for the clip If M1 is blank, mark on and seek to credit the correct information in the text

M2 The (forward) reaction / to the right is endothermic or takes in / absorbs heat OR The reverse reaction / to the left is exothermic or gives out / releases heat

M3 depends on correct M2 and must refer to temperature / heat M3 depends on a correct statement for M2

At high temperature, the (position of ) equilibrium shifts / moves left to right to oppose the increase in temperature For M3, the position of equilibrium shifts / moves to absorb heat OR to lower the temperature OR to cool down the reaction 3

(ii) M1 The reaction gets to equilibrium faster / in less time OR Produces a small yield faster / in less time OR Increases the rate (of reaction / of attainment of equilibrium) Mark independently

Page 71 of 76 M2

High pressure leads to one of the following • more particles / molecules in a given volume • particles / they are closer together • higher concentration of particles / molecules AND • more collisions in a given time / increased collision frequency Penalise M2 for reference to increased energy of the particles 2

(iii) M1 Increase in / more / large(r) / big(ger) surface area / surface sites Mark independently For M1 accept Éan increase in surface”

M2 increase in / more successful / productive / effective collisions (in a given time) (on the surface of the catalyst / with the nickel) For M2 not simply “more collisions” Ignore “the chance or likelihood” of collisions 2

(b) M1 No effect / None If M1 is incorrect CE = 0 for the clip If M1 is blank, mark on and seek to credit the correct information in the text

M2 requires a correct M1 Equal / same number / amount of moles / molecules / particles on either side of the equation OR 2 moles / molecules / particles on the left and 2 moles / molecules / particles on the right M2 depends on a correct statement for M1 In M2 not “atoms” 2 [9]

Q24. (a) Consider experiments 1 and 2: [B constant]

[A] increases × 3: rate increases by 32 therefore 2nd order with respect to A 1

Consider experiments 2 and 3:

[A] increases × 2: rate should increase × 22 but only increases × 2

Therefore, halving [B] halves rate and so 1st order with respect to B 1

Rate equation: rate = k[A]2[B] 1

(b) rate = k [C]2[D] therefore k = rate / [C]2[D] 1

Page 72 of 76

Allow consequential marking on incorrect transcription 1

mol–2 dm+6 s–1 Any order 1

Their k × (3.6 × 10–2)2 × 5.4 × 10–2 1

(d) Reaction occurs when molecules have E>Ea 1

Doubling T by 10 °C causes many more molecules to have this E 1

Whereas doubling [E] only doubles the number with this E 1

(e) Ea = RT(lnA – lnk) / 1000 Mark is for rearrangement of equation and factor of 1000 used correctly to convert J into kJ 1

–1 Ea = 8.31 × 300 (23.97 – (–5.03)) / 1000 = 72.3 (kJ mol ) 1 [12]

Q25. C [1]

Q26. (a) Method 1 Allow working throughout to 2sf M1 Moles of Mg = 0.396/24.3 = 0.0163 1

M2 Moles of CH3COOH = 0.600 × 30.0/1000 = 0.018 1

M3 Mark for showing Mg is in excess: either 0.018 mol of CH3COOH reacts with 0.009 mol of Mg OR 0.0163 mol of Mg reacts with 0.0326 mol of CH3COOH OR 0.0073 mol of Mg is in excess 1 If candidate gets 16.3 mol (as not converted mg to g) in method 1 or 3 then can only score 1 mark maximum (M2)

Page 73 of 76 Accept other valid calculations that show the Mg is in excess

Method 2 M1 Moles of CH3COOH = 0.600 × 30.0/1000 = 0.018

M2 Moles of Mg that would react with this = 0.009

M3 Mass of Mg needed = 24.3 × 0.009 = 0.219 g which is less than 0.396 g OR Moles of Mg = 0.0163 which is more than 0.009 required

Method 3 M1 Moles of Mg = 0.396/24.3 = 0.0163

M2 Moles of CH3COOH that would react with this = 0.0326

M3 Volume of CH3COOH needed = 0.0326 / 0.60 = 0.0543 dm3 (54.3 cm3) which is more than 0.030 dm3 (30 cm3)

(b) M1 Line starts at origin and is steeper 1

M2 (moles CH3COOH = 0.800 × 20/1000 = 0.016) line levels out on 8th line up (line below the original 9th line) M2 for line on 8th line on grid (original on 9th line) – allow some leniency so long as clear it ends at (or very close to) the 8th line; and line does not significantly wobble 1 [5]

Q27. (a) energy Ignore reference to • any units (e.g. J, kJ, J mol−1, kJ mol−1) • particles • molecules • kinetic NOT mean energy or average energy NOT E 1

(b) M1 maximum peak height is lower and displaced to the right of the original 1 M2 all of the following • starts at the origin but does not follow the original line • shows separation as soon as possible from the original line • crosses the original curve once only • similar area to original curve • an attempt has been made to draw the new curve correctly towards the energy axis above the original curve but not to touch the original curve (or axis) 1

(c) M1 an increase in the number/amount/proportion/fraction of molecules with E ≥ Ea / with activation energy or more molecules have E ≥ Ea / with activation energy

Page 74 of 76 or more molecules have enough / sufficient energy (to react) M1 Ignore • Molecules have more energy • More energetic collisions • More collisions

Allow E > Ea in place of E ≥ Ea Credit particles for molecules (but not atoms) Penalise for M1 reference to increased activation energy 1 M2 more successful / effective / productive collisions in a given time / period or higher rate of successful / effective / productive collisions or higher frequency of successful / effective / productive collisions M2 Must refer to both idea of successful / effective / productive collisions and the rate / frequency of collisions Ignore ‘chance of collision’ 1 [5]

Q28. C [1]

Q29. C [1]

Q30. B [1]

Q31. A [1]

Q32. D [1]

Q33. A [1]

Q34. D [1]

Page 75 of 76 Q35. (a)

M1 Curve is higher and displaced to the left M2 Only crosses the original curve once 2

(b) Rate of reaction decreases (no mark)

Fewer particles will have energy greater than or equal to the activation energy 1

Fewer successful collisions in a given time Less frequent successful collisions 1

Rate of reaction decreases (no mark)

Particles are spread further apart 1

Fewer collisions between gas particles so fewer successful collisions 1 [7]

Page 76 of 76 Seven Kings High School

Mass number and isotopes Name: ______Class: ______

Date: ______

Time: 233 minutes

Marks: 224 marks

Comments:

Page 1 Seven Kings High School

Q1. (a) Complete the following table.

Relative mass Relative charge

Neutron

Electron

(2)

(b) An atom has twice as many protons as, and four more neutrons than, an atom of 9Be. Deduce the symbol, including the mass number, of this atom.

...... (2)

(c) Draw the shape of a molecule of BeCl2 and the shape of a molecule of Cl2O. Show any lone pairs of electrons on the central atom. Name the shape of each molecule.

BeCl2 Cl2O

Name of shape ...... Name of shape ...... (4)

(d) The equation for the reaction between magnesium hydroxide and hydrochloric acid is shown below.

Mg(OH)2(s) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)

Calculate the volume, in cm3, of 1.00 mol dm–3 hydrochloric acid required to react completely with 1.00 g of magnesium hydroxide.

......

Page 2 Seven Kings High School ...... (4) (Total 12 marks)

Q2.(a) A sample of sulfur consisting of three isotopes has a relative atomic mass of 32.16. The following table gives the relative abundance of two of these isotopes.

Mass number of isotope 32 33

Relative abundance / % 91.0 1.8

Use this information to determine the relative abundance and hence the mass number of the third isotope. Give your answer to the appropriate number of significant figures.

Mass number = ...... (4)

(b) Describe how ions are formed in a time of flight (TOF) mass spectrometer.

......

...... (2)

Page 3 Seven Kings High School Explain why it is necessary to ionise molecules when measuring their mass in a TOF mass spectrometer.

......

...... (2) (Total 8 marks)

Q3.Assuming that chlorine exists as two isotopes, and that hydrogen and carbon exist as one isotope each, how many molecular ion peaks will be shown in the mass spectrum of

C4H6Cl4?

A 2

B 3

C 4

D 5 (Total 1 mark)

Q4. (a) State the relative charge and relative mass of a proton, of a neutron and of an electron. In terms of particles, explain the relationship between two isotopes of the same element. Explain why these isotopes have identical chemical properties. (7)

(b) Define the term relative atomic mass. An element exists as a mixture of three isotopes. Explain, in detail, how the relative atomic mass of this element can be calculated from data obtained from the mass spectrum of the element. (7) (Total 14 marks)

Page 4 Seven Kings High School

Q5. (a) One isotope of sodium has a relative mass of 23.

(i) Define, in terms of the fundamental particles present, the meaning of the term isotopes.

......

(ii) Explain why isotopes of the same element have the same chemical properties.

......

(iii) Calculate the mass, in grams, of a single atom of this isotope of sodium. (The Avogadro constant, L, is 6.023 × 1023 mol–1)

......

...... (5)

(b) Give the electronic configuration, showing all sub-levels, for a sodium atom.

...... (1)

......

...... (1)

Page 5 Seven Kings High School (d) An atom has half as many protons as an atom of 28Si and also has six fewer neutrons than an atom of 28Si. Give the symbol, including the mass number and the atomic number, of this atom.

...... (2) (Total 9 marks)

Q6. (a) Complete the following table.

Relative mass Relative charge

Proton

Electron

(2)

(b) An atom of element Q contains the same number of neutrons as are found in an atom of 27A1. An atom of Q also contains 14 protons.

(i) Give the number of protons in an atom of 27A1.

......

(ii) Deduce the symbol, including mass number and atomic number, for this atom of element Q.

...... (3)

......

...... (2)

(d) The table below gives the relative abundance of each isotope in a mass spectrum of a sample of magnesium.

Page 6 Seven Kings High School m/z 24 25 26

Relative abundance (%) 73.5 10.1 16.4

Use the data above to calculate the relative atomic mass of this sample of magnesium. Give your answer to one decimal place.

......

...... (2)

(e) State how the relative molecular mass of a covalent compound is obtained from its mass spectrum.

......

...... (1) (Total 10 marks)

Q7.Chlorine has two isotopes, 35Cl and 37Cl. The number of molecular ion peaks in the mass spectrum of a sample of Cl2 is

A 2

B 3

C 4

D 5 (Total 1 mark)

Q8. In one model of atomic structure, the atom has a nucleus surrounded by electrons in levels and sub-levels.

Page 7 Seven Kings High School (a) Define the term atomic number.

...... (1)

(b) Explain why atoms of an element may have different mass numbers.

...... (1)

Relative m/z 82 83 84 86

Relative abundance / % 12 12 50 26

(i) Name an instrument which is used to measure the relative abundance of isotopes.

......

(ii) Define the term relative atomic mass.

......

(iii) Calculate the relative atomic mass of this sample of krypton.

......

...... (5)

(d) Give the complete electronic configuration of krypton in terms of s, p and d sub-levels.

...... (1)

Page 8 Seven Kings High School (e) In 1963, krypton was found to react with fluorine. State why this discovery was unexpected.

...... (1)

(f) Use a suitable model of atomic structure to explain the following experimental observations.

(i) The first ionisation energy of krypton is greater than that of bromine.

......

(ii) The first ionisation energy of aluminium is less than the first ionisation energy of magnesium.

......

...... (4) (Total 13 marks)

Q9. Mass spectrometry can be used to identify isotopes of elements.

(a) (i) In terms of fundamental particles, state the difference between isotopes of an element.

......

...... (1)

(ii) State why isotopes of an element have the same chemical properties.

......

...... (1)

Page 9 Seven Kings High School

(b) Give the meaning of the term relative atomic mass.

......

(Extra space)......

...... (2)

(c) The mass spectrum of element X has four peaks. The table below gives the relative abundance of each isotope in a sample of element X.

m/z 64 66 67 68

Relative abundance 12 8 1 6

(i) Calculate the relative atomic mass of element X. Give your answer to one decimal place.

......

...... (3)

(ii) Use the Periodic Table to identify the species responsible for the peak at m/z = 64

...... (2)

(d) Suggest one reason why particles with the same mass and velocity can be deflected by different amounts in the same magnetic field.

......

Page 10 Seven Kings High School ...... (1)

(e) Explain how the detector in a mass spectrometer enables the abundance of an isotope to be measured.

......

(Extra space) ......

...... (2) (Total 12 marks)

Q10. In 1913 Niels Bohr proposed a model of the atom with a central nucleus, made up of protons and neutrons, around which electrons moved in orbits. After further research, the model was refined when the existence of energy levels and sub-levels was recognised.

(a) Complete the following table for the particles in the nucleus.

Particle Relative charge Relative mass

proton

neutron

(2)

(b) State the block in the Periodic Table to which the element tungsten, W, belongs.

...... (1)

(i) Deduce the number of protons in 182W

......

Page 11 Seven Kings High School (1)

(ii) Deduce the number of neutrons in 186W

...... (1)

(d) In order to detect the isotopes of tungsten using a mass spectrometer, a sample containing the isotopes must be vaporised and then ionised.

(i) Give two reasons why the sample must be ionised.

1 ......

2 ...... (2)

(ii) State what can be adjusted in the mass spectrometer to enable ions formed by the different isotopes to be directed onto the detector.

...... (1)

(e) State and explain the difference, if any, between the chemical properties of the isotopes 182W and 186W

Difference ......

Explanation ......

...... (2)

(f) The table below gives the relative abundance of each isotope in the mass spectrum of a sample of tungsten. m/z 182 183 184 186

Relative abundance /% 26.4 14.3 30.7 28.6

Use the data above to calculate a value for the relative atomic mass of this sample of tungsten. Give your answer to 2 decimal places.

......

...... Page 12 Seven Kings High School ...... (2) (Total 12 marks)

Q11. A mass spectrometer can be used to investigate the isotopes in an element.

(a) Define the term relative atomic mass of an element.

......

...... (2)

(b) Element X has a relative atomic mass of 47.9

Identify the block in the Periodic Table to which element X belongs and give the electron configuration of an atom of element X.

Calculate the number of neutrons in the isotope of X which has a mass number 49

......

...... (3)

Use this spectrum to calculate the relative atomic mass of Z, giving your answer to one decimal place.

Identify element Z.

Page 13 Seven Kings High School

......

...... (4)

(d) State how vaporised atoms of Z are converted into Z+ ions in a mass spectrometer.

State and explain which of the Z+ ions formed from the isotopes of Z in part (c) will be deflected the most in a mass spectrometer.

......

...... (4)

(e) Explain briefly how the relative abundance of an ion is measured in a mass

Page 14 Seven Kings High School spectrometer.

......

...... (2) (Total 15 marks)

Q12.The manufacturer supplying concentrated ethanoic acid for the production of vinegar also supplied other acids. The label had come off a batch of one of these other acids. A sample of this unknown acid was analysed and found to contain 54.5% of carbon and 9.10% of hydrogen by mass, the remainder being oxygen.

(a) Use these data to calculate the empirical formula of the unknown acid. Show your working.

......

...... (3)

(b) A sample of the unknown acid was analysed in a mass spectrometer. The mass spectrum obtained is shown below.

Page 15 Seven Kings High School

Use the mass spectrum to determine the Mr of the unknown acid.

...... (1)

(If you could not answer part (b), you should assume that the Mr of the acid is 132.0 but this is not the correct value.) Show your working.

......

...... (2) (Total 6 marks)

Q13. (a) Define the term relative atomic mass.

An organic fertiliser was analysed using a mass spectrometer. The spectrum showed that the nitrogen in the fertiliser was made up of 95.12% 14N and 4.88% 15N

Calculate the relative atomic mass of the nitrogen found in this organic fertiliser. Give your answer to two decimal places.

......

Page 16 Seven Kings High School ......

......

...... (4)

(b) In a mass spectrometer, under the same conditions, 14N+ and 15N+ ions follow different paths. State the property of these ions that causes them to follow different paths.

State one change in the operation of the mass spectrometer that will change the path of an ion.

......

...... (2)

State and explain whether or not you would expect the chemical reactions of the nitrogen compounds in the synthetic fertiliser to be different from those in the organic fertiliser. Assume that the nitrogen compounds in each fertiliser are the same.

......

...... (2) (Total 8 marks)

Page 17 Seven Kings High School

Q14.(a) State the meaning of the term mass number of an isotope.

......

...... (1)

(b) Give the symbol of the element that has an isotope with a mass number of 68 and has 38 neutrons in its nucleus.

...... (1)

(i) State what happens to the sample in the parts labelled P and Q.

P ......

Q ...... (2)

(ii) In a mass spectrometer, the isotopes of an element are separated. Two measurements for each isotope are recorded on the mass spectrum.

State the two measurements that are recorded for each isotope.

Measurement 1 ......

Measurement 2 ...... Page 18 Seven Kings High School (2)

(d) A sample of element R contains isotopes with mass numbers of 206, 207 and 208 in a 1:1:2 ratio of abundance.

(i) Calculate the relative atomic mass of R. Give your answer to one decimal place.

......

...... (3)

(ii) Identify R.

...... (1)

(iii) All the isotopes of R react in the same way with concentrated nitric acid.

State why isotopes of an element have the same chemical properties.

......

(Extra space) ......

...... (1) (Total 11 marks)

Q15. Define the term mass number of an atom.

The mass number of an isotope of nitrogen is 15. Deduce the number of each of the fundamental particles in an atom of 15N

......

Page 19 Seven Kings High School ......

......

...... (Total 3 marks)

Q16.The manufacture of food grade phosphoric acid for use in cola drinks begins with the production of pure white phosphorus from the mineral fluoroapatite, Ca5F(PO4)3

(a) Complete the following equation for the manufacture of phosphorus.

....Ca5F(PO4)3 + 9SiO2 + ....C 9CaSiO3 + CaF2 + ....CO + ... .P (1)

(b) As the phosphorus cools, it forms white phosphorus, P4

Give the oxidation state of phosphorus in each of the following.

P4 ......

H3PO4 ...... (2)

(c) Fertiliser grade phosphoric acid is manufactured from sulfuric acid and calcium phosphate. Use the following precise relative atomic mass data to show how mass spectrometry

can be used to distinguish between pure sulfuric acid (H2SO4) and pure phosphoric

acid (H3PO4) which both have Mr = 98 to two significant figures.

Atom Precise relative atomic mass

1H 1.00794

16O 15.99491

31P 30.97376

32S 32.06550

Page 20 Seven Kings High School ......

......

...... (1)

(d) Concentrated phosphoric acid is used as a catalyst in the hydration of propene to

form the alcohol CH3CH(OH)CH3 as the main organic product. The industrial name for this alcohol is isopropyl alcohol.

(i) State the meaning of the term catalyst.

......

(Extra space) ......

...... (1)

(ii) State the meaning of the term hydration.

......

(Extra space) ......

...... (1)

(iii) Write an equation for the hydration of propene to form isopropyl alcohol. Give the IUPAC name for isopropyl alcohol.

Equation ......

IUPAC name ...... (2) (Total 8 marks)

Page 21 Seven Kings High School

Q17.The mass spectrum of a sample of krypton taken from a meteorite is shown below.

(a) Use this spectrum to calculate the relative atomic mass of this sample of krypton. Give your answer to one decimal place.

Explain why the value you have calculated is slightly different from the relative atomic mass given in the Periodic Table.

......

(Extra space) ......

......

...... (4)

Page 22 Seven Kings High School

(b) State how krypton is ionised in the mass spectrometer.

Write an equation, including state symbols, to show the reaction that occurs when the first ionisation energy of Kr is measured.

Sometimes the mass spectrum of Kr has a very small peak with an m/z value of 42. Explain the occurrence of this peak.

......

(Extra space) ......

......

...... (5) (Total 9 marks)

Q18.The element rubidium exists as the isotopes 85Rb and 87Rb

(a) State the number of protons and the number of neutrons in an atom of the isotope 85Rb

Number of protons ......

Number of neutrons ...... (2)

(b) (i) Explain how the gaseous atoms of rubidium are ionised in a mass spectrometer

Page 23 Seven Kings High School ......

......

...... (2)

(ii) Write an equation, including state symbols, to show the process that occurs when the first ionisation energy of rubidium is measured.

...... (1)

Element sodium potassium rubidium

First ionisation 494 418 402 energy / kJ mol–1

State one reason why the first ionisation energy of rubidium is lower than the first ionisation energy of sodium.

......

...... (1)

(d) (i) State the block of elements in the Periodic Table that contains rubidium.

...... (1)

(ii) Deduce the full electron configuration of a rubidium atom.

...... (1)

Page 24 Seven Kings High School

(e) A sample of rubidium contains the isotopes 85Rb and 87Rb only. The isotope 85Rb has an abundance 2.5 times greater than that of 87Rb

Calculate the relative atomic mass of rubidium in this sample. Give your answer to one decimal place.

......

...... (3)

(f) By reference to the relevant part of the mass spectrometer, explain how the abundance of an isotope in a sample of rubidium is determined.

Name of relevant part ......

Explanation ......

......

...... (2)

(g) Predict whether an atom of 88Sr will have an atomic radius that is larger than, smaller than or the same as the atomic radius of 87Rb. Explain your answer.

Atomic radius of 88Sr compared to 87Rb ......

Explanation ......

......

...... (3) (Total 16 marks)

Page 25 Seven Kings High School Q19.The mass spectrum of the isotopes of element X is shown in the diagram.

m / z

(a) Define the term relative atomic mass.

......

...... (2)

(b) Use data from the diagram to calculate the relative atomic mass of X.

Give your answer to one decimal place.

......

...... (3)

...... (1)

Page 26 Seven Kings High School

(d) Identify which one of the isotopes of X is deflected the most in the magnetic field of a mass spectrometer. Give a reason for your answer.

Isotope ......

Reason ...... (2)

(e) In a mass spectrometer, the relative abundance of each isotope is proportional to the current generated by that isotope at the detector.

Explain how this current is generated.

......

...... (2)

(f) X and Zn are different elements.

......

Explain why the chemical properties of 70X and 70Zn are different. (1) (Total 11 marks)

Q20.(a) Table 1 shows some data about fundamental particles in an atom. Table 1

Particle proton neutron electron

Mass / g 1.6725 × 10–24 1.6748 × 10–24 0.0009 × 10–24

(i) An atom of hydrogen can be represented as 1H

Use data from Table 1 to calculate the mass of this hydrogen atom.

......

Page 27 Seven Kings High School (1)

(ii) Which one of the following is a fundamental particle that would not be deflected by an electric field?

A electron

B neutron

C proton

Write the correct letter, A, B or C, in the box.

(1)

(b) A naturally occurring sample of the element boron has a relative atomic mass of 10.8. In this sample, boron exists as two isotopes, 10B and 11B

(i) Calculate the percentage abundance of 10B in this naturally occurring sample of boron.

......

...... (2)

(ii) State, in terms of fundamental particles, why the isotopes 10B and 11B have similar chemical reactions.

......

...... (1)

Page 28 Seven Kings High School

Table 2

First Second Third Fourth Fifth

Ionisation energy / kJ mol–1 799 2420 25 000 32 800

(1)

(d) Write an equation to show the process that occurs when the second ionisation energy of boron is measured. Include state symbols in your equation.

...... (1)

(e) Explain why the second ionisation energy of boron is higher than the first ionisation energy of boron.

......

...... (1) (Total 8 marks)

Q21.Tellurium is the element with atomic number of 52

(a) Using information from the Periodic Table, complete the electron configuration of tellurium.

[Kr] ...... (1)

(b) The mass spectrum of a sample of tellurium is shown in the graph.

Page 29 Seven Kings High School

(i) Use the graph to calculate the relative atomic mass of this sample of tellurium. Give your answer to one decimal place.

......

...... (3)

(ii) Suggest what might cause the relative atomic mass of this sample to be different from the relative atomic mass given in the Periodic Table.

......

...... (1)

(d) State the m / z value of the ions that produce the biggest current at the detector when the spectrum in the graph is recorded. Give a reason for your answer.

m / z value ......

Page 30 Seven Kings High School Reason ......

......

...... (2)

(e) The mass spectrum of tellurium also has a small peak at m / z = 64

Explain the existence of this peak.

......

...... (2)

(f) Predict whether the atomic radius of 124Te is larger than, smaller than or the same as the atomic radius of 130Te Explain your answer.

Atomic radius of 124Te compared to 130Te ......

Explanation ......

......

...... (2) (Total 12 marks)

Q22.A sample of ethanedioic acid was treated with an excess of an unknown alcohol in the presence of a strong acid catalyst. The products of the reaction were separated and analysed in a time of flight (TOF) mass spectrometer. Two peaks were observed at m / z = 104 and 118.

(a) Identify the species responsible for the two peaks.

......

Page 31 Seven Kings High School ...... (2)

(b) Outline how the TOF mass spectrometer is able to separate these two species to give two peaks.

......

...... (4) (Total 6 marks)

Q23.Which of these atoms has the smallest number of neutrons?

3 A H

4 B He

5 C He

4 D Li

(Total 1 mark)

Q24.(a) Explain how ions are accelerated, detected and have their abundance determined in a time of flight (TOF) mass spectrometer.

......

Page 32 Seven Kings High School ......

...... (3)

(b) Calculate the mass, in kg, of a single 52Cr+ ion. Assume that the mass of a 52Cr+ ion is the same as that of a 52Cr atom.

(The Avogadro constant L = 6.022 × 1023 mol−1)

......

...... (1)

Calculate the velocity of the ion using the equation.

(m = mass/kg and v = velocity/ms−1)

......

...... (2)

(d) Bromine has two isotopes, 79Br and 81Br, in approximately equal abundance. In a + TOF mass spectrometer bromine forms ions with formula [Br2]

Sketch the pattern of peaks you would expect to see in the mass spectrum of a sample of bromine.

Page 33 Seven Kings High School

(2)

(e) A sample of xenon has Ar = 131.31. The sample consists of four isotopes. The abundances of three of the isotopes are shown in the table below. The data for one of the isotopes, mXe, is missing.

Isotope 129Xe 131Xe 132Xe mXe % To be 28.0 25.0 27.0 abundance calculated

Use the data to calculate the abundance of isotope mXe and calculate m, the mass number of mXe. Show your working.

......

...... (4) (Total 12 marks)

Q25.Ions of two isotopes of iron are

53Fe2+ 56Fe2+

Which statement is correct?

Page 34 Seven Kings High School

A The ions of both the isotopes have the electronic

configuration 1s22s22p63s23p64s23d6

B The ions of both the isotopes contains 26 neutrons

53 2+ 56 2+ C Fe has fewer protons than Fe

D After acceleration to the same kinetic energy 56Fe2+

will move more slowly than 53Fe2+

(Total 1 mark)

Q26.The successive ionisation energies for element X are shown in the following graph.

Which element is X?

A Nitrogen

B Phosphorus

C Aluminium

D Boron

(Total 1 mark)

Q27.This question is about electron configuration.

(a) Give the full electron configuration of an Al atom and of a Cr3+ ion.

Al atom......

Cr3+ ion ......

Page 35 Seven Kings High School (2)

(b) Deduce the formula of the ion that has a charge of 2+ with the same electron configuration as krypton.

...... (1)

(c) Deduce the formula of the compound that contains 2+ ions and 3− ions that both have the same electron configuration as argon.

...... (1) (Total 4 marks)

Page 36 Seven Kings High School

M1. (penalty for sig fig error =1 mark per question)

(a) neutron: relative mass = 1 relative charge = 0 (not ‘neutral’) 1

electron: relative mass = 1/1800 → 0/negligible or

5.56 × 10–4 → 0 relative charge = –1 1

(b) 17O/O17 mass number (Do not accept 17.0) 1

oxygen symbol ‘O’ (if ‘oxygen’ + — ‘mass number = 17’(1)) (if ‘oxygen’+ — ‘mass number = 17’(0)) (if at N 0 given but ≠ 8, treat as ‘con’ for M2) (if lp on Be, diagram = 0) (ignore bond angles) (not dot and cross diagrams) 1

(c)

QoL Linear (1) bent / V-shaped / angular (1) (mark name and shape independently) (accept (distorted) tetrahedral) (if balls instead of symbols, lose M1 – can award M2) (penalise missing ‘Cl’ once only) (not ‘non-linear’) 2

0 (d) Mr (Mg(NO3)2 = 58(.3) (if At N used, lose M1 and M2) 1

moles Mg(OH)2 = 0.0172 (conseq on wrong M2) (answer to 3+ s.f.)

Page 37 Seven Kings High School 1

moles HCl = 2 × 0.0172 = 0.0344 or 0.0343 (mol) (process mark) 1

vol HCl = = 34.3 – 34.5 (cm3) (unless wrong unit) (if candidate used 0.017 or 0.0171 lose M2) (just answer with no working, if in range = (4). if, say, 34 then =(2)) (if not 2:1 ratio, lose M3 and M4) (if work on HCl, CE = 0/4) 1 [12]

M2.(a) Abundance of third isotope = 100 – 91.0 –1.8 = 7.2% 1

= 32.16 1

7.2y = 32.16 × 100 – 32 × 91 – 33 × 1.8 = 244.6 1

y = 244.6 / 7.2 = 33.97

y = 34 Answer must be rounded to the nearest integer 1

(b) (for electrospray ionisation)

A high voltage is applied to a sample in a polar solvent 1

the sample molecule, M, gains a proton forming MH+ 1

Page 38 Seven Kings High School OR

(for electron impact ionisation)

the sample is bombarded by high energy electrons 1

the sample molecule loses an electron forming M+ 1

Only ions will create a current when hitting the detector 1 [8]

M3.D [1]

M4. (a) Proton: mass 1, charge + 1 (1) Neutron: mass 1, charge 0 (1) Electron mass 1/1840, charge -1 (1) Allow mass = 0, or negligible, or 1/1800 to 1/2000

Isotopes have the same number of protons (1) OR atomic number

different number of neutrons (1)

Isotopes have the same electronic configuration (1) OR same number of electrons

Chemical properties depend on electrons (1) 7

(b) ×12 (1)

OR × 12 or in words

Page 39 Seven Kings High School Spectrum gives (relative) abundance (1) OR % or amount

And m/z (1) Multiply m/z by relative abundance for each isotope (1)

Allow instead of m/z mass no, Ar or actual value from example

Sum these values (1) Divide by the sum of the relative abundances (1) only award this mark if previous 2 given Max 2 if e.g. has only 2 isotopes 7 [14]

M5. (a) (i) Atoms with the same number of protons / proton number (1) NOT same atomic number

with different numbers of neutrons (1) NOT different mass number / fewer neutrons

(ii) Chemical properties depend on the number or amount of (outer) electrons (1) OR, isotopes have the same electron configuration / same number of e–

(iii) 23/6.023 × 1023 (1) CE = 0 if inverted or multiplied

tied to M1 3.8(2) × 10–23 [2-5 sig figs] (1) 5

(b) 1s2 2s2 2p6 3s1 (1) accept subscripted figures 1

(c) Highest energy e– / outer e–s / last e– in (3)d sub-shell (1) OR d sub-shell being filled / is incomplete OR highest energy sub-shell is (3)d NOT transition element / e– configuration ends at 3d Q of L 1

Page 40 Seven Kings High School

(d) N correct symbol (1)

allow

Mass number = 15 AND atomic number = 7 (1) 2 [9]

M6. (a) Proton mass = 1 charge = +1 Electron mass 1/1800 Or 5.6 × 10–4 charge = –1 (Do not accept +1 for proton mass or ‘g’ units) 2

(b) (i) 13 1

(ii) Si 1

Mass number = 28 and atomic number = 14 (Do not accept 28.1 or 28.0 or ‘Silicon’) 5

(c) Mean (average) mass of an atom / all the isotopes 1/12th mass of atom of 12C Or Mass of 1 mole of atoms of an element (1) 1/12th mass of 1 mole of 12C (1) Or Average mass of an atom / all the isotopes (1) relative to the mass of a 12C atom taken as exactly 12 / 12.000 (1) (Penalise ‘weight’ once only) (Ignore ‘average’ mass of 12C) (Do not allow ‘mass of average atom’) 2

(d) Ar = (24 × 0.735) + (25 × 0.101) + (26 × 0.164) 1 = 24.4 1 (mark M2 conseq on transcription error or incorrect addition of %)

(e) Mr = highest m/z value 1

Page 41 Seven Kings High School (NOT ‘highest/largest/right-hand’ peak) 3 [10]

M7.B [1]

M8. (a) Number of protons in the nucleus 1

(b) They may have different numbers of neutrons 1

(ii) × 12 2

(iii) Ar = 1

= (82 × 12 + 83 × 12 + 84 × 50 + 86 × 26)/100 = 84.16 1

(d) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 1

(e) Krypton was thought to be an inert gas (or has 8 electrons in outer shell) 1

(f) (i) Krypton has more protons than bromine 1

But its outer electrons are in the same shell (or have similar shielding)

Page 42 Seven Kings High School 1

(ii) Al electron is in a 3p orbital, magnesium in 3s 1

Energy of 3p is greater than 3s 1 [13]

M9. (a) (i) Different number / amount of neutrons Not different neutrons Ignore same protons and/or electrons CE incorrect statement relating to protons / electrons 1

(ii) Same electron configuration / same number of electrons (in the outer shell) Ignore same no of protons Ignore electrons determine chemical properties CE if wrong statement relating to protons / neutrons 1

(b) Average mass of 1 atom (of an element) 1/12 mass atom of 12C

Average/mean mass of atoms of an element 1/12 mass of one atom of 12C

(Average) mass of one mole of atoms 1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes 1/12 mass of one atom of 12C

Page 43 Seven Kings High School Average mass of an atom/isotope compared to C-12 on a scale in which an atom of C-12 has a mass of 12 If moles and atoms mixes Max = 1 Mark top and bottom line independently 1/12 on bottom line can be represented as x 12 on top line This expression = 2 marks 2

= 65.6 If not 27 max 1 mark (for top line) Mark is for dividing by 27 or string If evidence of arithmetic or transcription error seen in M1 or M2 allow consequential M3 and consequential (c)(ii) 65.6 = 3 marks 3

(ii) 64Zn+ M1 for identifying Zn / zinc M2 is for the + sign and the 64 M2 is dependent on M1 2

(d) Size of the charge (on the ion) / different charges / different m/z Allow forms 2+ ions QWC 1

(e) (ions hit detector and) cause current/(ions) accept electrons/cause electron flow/electric pulse caused bigger current = more of that isotope/current proportional to abundance Implication that current depends on the number of ions M2 dependent on M1 2 [12]

Page 44 Seven Kings High School M10. (a) Particle Relative Charge Relative mass

Proton +1 1 1

Neutron 0 1 1

Need +1 for proton

(b) d block/ D block; Or D or d 1

(ii) 112; Not 112.0 1

(d) (i) To accelerate/ make go faster; 1

To deflect/ to bend the beam; Any order Not just attract to negative plate 1

(ii) Electromagnet / magnet / electric field /accelerating potential or voltage; Not electric current Not electronic field 1

(e) None/ nothing; If blank mark on. If incorrect CE = 0 1

Page 45 Seven Kings High School Same number of electrons (in outer orbital/shell)/ both have 74 electrons/same electron configuration; Not just electrons determine chemical properties Ignore protons and neutrons unless wrong statement. 1

(f) ; If transcription error then M1 = AE = –1 and mark M2 consequentially 1

= 183.90; allow range from 183.90 – 184.00; 1 [12]

(a) Average/mean mass of (1) atom(s) (of an element) 1/12 mass of one atom of 12C 1 If moles and atoms mixes Max = 1 1

(Average) mass of one mole of atoms 1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes 1/12 mass of one atom of 12C

Average mass of an atom/isotope compared to C-12 on a scale in which an atom of C-12 has a mass of 12 This expression = 2 marks

(b) d block Allow 3d/D Other numbers lose M1

Page 46 Seven Kings High School Ignore transition metals 1

[Ar] 3d24s2 1 Can be written in full Allow subscripts 3d2 and 4s2 can be in either order

27 1

(c)

(= 1550) 1

(or ∑ their abundances) If one graph reading error lose M1 and allow consequential M2 and M3. If 2 GR errors penalise M1 and M2 but allow consequential M3 If not 17 or ∑ their abundances lose M2 and M3 1

= 91.2 91.2 = 3 marks provided working shown. 1

Zr/Zirconium M4 -allow nearest consequential element from M3 accept Zr in any circumstance 1

(d) High energy electrons/bombarded or hit with electrons accept electron gun 1

knocks out electron(s) (to form ions) 1

Z+ = 90 deflected most If not 90 lose M3 and M4 If charge is wrong on 90 isotope lose M3 only Accept any symbol in place of Z 1

since lowest mass/lowest m/z Allow lightest 1

Page 47 Seven Kings High School

(e) (ions hit detector and) cause current/(ions) accept electrons/cause electron flow QWC 1

bigger current = more of that isotope/current proportional to abundance Implication that current depends on the number of ions 1 [15]

M12.(a) Percentage of oxygen is 36.4% % of oxygen stated or shown in calculation. 1

Correct calculation of ratios (C 4.54, H 9.10, O 2.28)

Mark is for correct method, dividing % by Ar 1

Empirical formula C2H4O Allow consequential answer from wrong percentage of oxygen (max 2 marks). 1

(b) 88 Accept 88.0 Do not penalise correct answer in g. 1

If use 132 / 44 = 3, molecular formula C6H12O3 scores 2 marks. 1

Molecular formula is C4H8O2

Page 48 Seven Kings High School Accept consequential answers from (a) and (b) 1 [6]

M13. (a) Average/mean mass of (1) atom(s) (of an element) 1

1/12 mass of one atom of 12C Accept answer in words Can have top line × 12 instead of bottom line ÷ 12 1

(Average) mass of one mole of atoms 1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes 1/12 mass of one atom of 12C

Average mass of an atom/isotope compared to C-12 on a scale in which an atom of C-12 has a mass of 12

Allow 95.12 + 4.88 instead of 100 1

= 14.05 If not to 2 d.p. then lose last mark Not 14.04 1

(b) 15N is heavier/15N has a bigger m/z/different m/z values Not different no’s of neutrons Not ionisation potential 1

Electromagnet/electric field/magnet/accelerating potential or voltage/electric current 1

Page 49 Seven Kings High School Same no of electrons (in outer orbital/shell/sub shell)/same electron configuration M2 dependent on M1 Not just electrons determine chemical properties Ignore protons 1 [8]

M14.(a) (Total number of) protons and neutrons (in nucleus of atom) (number of) nucleons 1

(b) Zn Do not allow Zn−1 or Zn+1 or ZN Ignore numbers 1

Q = accelerate (sample) Allow speeds (ions) up Penalise molecules / atoms 1

(ii) m / z Allow mass / charge 1

(relative) abundance / (relative) intensity QoL Allow M1 + M2 in any order 1

Page 50 Seven Kings High School

(d) (i) M1 = topline 1

M2 = ÷ 4 1

= 207.3 Only 207.3 = 3 marks 1

(ii) Lead / Pb Not PB 1

(iii) Same number of electrons (in outer shell) / same electronic configuration Ignore electrons determine chemical properties Ignore reference to p and n if correct Penalise if incorrect 1 [11]

M15. Mass number = number of protons + neutrons (in the nucleus/atom) Not in a substance or compound or element 1

7 protons and 7 electrons 1

8 neutrons 1 [3]

Page 51 Seven Kings High School

M16. (a) 2Ca5F(PO4)3+ 9SiO2 +15C 9CaSiO3 + CaF2 +15CO + 6P 1

(b) M1 (P4 =) 0

M2 (H3PO4 =) (+) 5 Accept Roman numeral V for M2 2

Mr = 2(1.00794) + 32.06550 + 4(15.99491) = 98.06102 or 98.0610 or 98.061 or 98.06 or 98.1 Calculations not required

and

H3PO4

Mr = 3(1.00794) + 30.97376 + 4(15.99491) = 97.97722 or 97.9772 or 97.977 or 97.98 or 98.0 1

(d) (i) A substance that speeds up a reaction OR alters / increases the rate of a reaction AND is chemically unchanged at the end / not used up. Both ideas needed Ignore reference to activation energy or alternative route. 1

(ii) The addition of water (QoL ) to a molecule / compound QoL- for the underlined words 1

(iii) M1 CH3CH=CH2 + H2O CH3CH(OH)CH3

(C3H6) For M1 insist on correct structure for the alcohol but credit correct equations using either C3H6 or double bond not given.

M2 propan-2-ol 2 [8]

Page 52 Seven Kings High School

M17.(a)

M1 for the top line M2 is for division by 17 1

= 84.0 Not 84 No consequential marking from M1 or M2 Ignore units 1

The Ar in the Periodic table takes account of the other isotopes /different amounts of isotopes (or words to that effect regarding isotopes) Award independently Comparison implied Isotope(s) alone, M4 = 0 1

(b) (Beam of electrons from) an electron gun / high speed / high energy electrons 1

Knocks out electron(s) (to form a positive ion) 1

Kr(g) + e– → Kr+(g) + 2e(–) State symbols must clearly be (g) 1

Kr(g) → Kr+(g) + e(–) / Kr(g) – e(–) → Kr+(g)

Page 53 Seven Kings High School The 84Kr isotope One mark for identifying the 84 isotope 1

Has 2 electrons knocked out / gets a 2+ charge One mark for the idea of losing 2 electrons (from this isotope) 1 [9]

M18. (a) 37 These answers only. Allow answers in words. 1

48 Ignore any sum(s) shown to work out the answers. 1

(b) (i) Electron gun / high speed/high energy electrons Not just electrons. Not highly charged electrons. 1

Knock out electron(s) Remove an electron. 1

(ii) Rb(g) → Rb+(g) + e(–) OR Rb(g) + e(–) → Rb+(g) + 2e(–) OR Rb(g) - e(–) → Rb+(g) Ignore state symbols for electron. 1

Page 54 Seven Kings High School energy level/ More shielding in Rb / less attraction of nucleus in Rb for outer electron / more shells Answer should refer to Rb not Rb molecule If converse stated it must be obvious it refers to Na Answer should be comparative. 1

(d) (i) s / block s / group s Only 1

(ii) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 Allow 3d10 before 4s2 Allow in any order. 1

(e) (85 × 2.5) + 87 ×1 3.5 M1 is for top line 1 1

= 85.6 Only 1

(58 × 5) + 87 ×2 7 M185Rb 71.4% and 87Rb 28.6% M2 divide by 100 1 1

85.6 M3 = 85.6 1

(f) Detector Mark independently Allow detection (plate). 1

Current / digital pulses / electrical signal related to abundance Not electrical charge.

Page 55 Seven Kings High School 1

(g) Smaller Chemical error if not smaller, CE = 0/3 If blank mark on. 1

Bigger nuclear charge / more protons in Sr Not bigger nucleus. 1

Similar/same shielding QWC (Outer) electron entering same shell/sub shell/orbital/same number of shells. Do not allow incorrect orbital. 1 [16]

M19.(a) Average / mean mass of 1 atom (of an element) 1/12 mass of one atom of 12C If moles and atoms mixed, max = 1 1

Mark top and bottom line independently. All key terms must be present for each mark. 1

Average / mean mass of atoms of an element 1/12 mass of one atom of 12C

Average / mean mass of atoms of an element ×12 mass of one atom of 12C

OR Page 56 Seven Kings High School (Average) mass of one mole of atoms 1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes 1/12 mass of one atom of 12C

Average mass of an atom / isotope (compared to C−12) on a scale in which an atom of C−12 has a mass of 12 This expression = 2 marks.

(b) 1 1

= 72.4 72.4 only 1

(d) 70 If M1 incorrect or blank CE = 0/2 Ignore symbols and charge even if wrong. 1

Lowest mass / lowest m/z Accept lightest. Accept fewest neutrons. 1

(e) Electron(s) transferred / flow (at the detector) M1 must refer to electron flow at the detector. If M1 incorrect CE = 0/2 1

Page 57 Seven Kings High School

(From detector / plate) to the (+) ion Do not allow from a charged plate. 1

(f) They do not have the same electron configuration / they have different number of electrons (in the outer shell) Ignore electrons determine the properties of an atom. Ignore they are different elements or different number of protons. 1 [11]

M20.(a) (i) 1.6734 × 10−24 (g) Only.

1.6734 × 10−27 kg Not 1.67 × 10−24 (g). 1

(ii) B 1

(b) (i) = 10.8

OR ratio 10:11 = 1:4 OR 20:80 etc Allow idea that there are 5 × 0.2 divisions between 10 and 11. 1

abundance of 10B is 20(%)

= 10.8

10x + 1100 − 11x = 1080

x = 1100 − 1080 = 20%

∴ Page 58 Seven Kings High School Correct answer scores M1 and M2. 1

(ii) Same number of electrons (in outer shell or orbital) Ignore electrons determine chemical properties.

Same electronic configuration / arrangement Ignore protons unless wrong. 1

(d) B+(g) B2+(g) + e(−)

B+(g) − e(−) B2+(g)

B+(g) + e(−) B2+(g) + 2e(−) Ignore state symbol on electron even if wrong. 1

(e) Electron being removed from a positive ion (therefore needs more energy) / electron being removed is closer to the nucleus Must imply removal of an electron. Allow electron removed from a + particle / species or from a 2+ ion. Not electron removed from a higher / lower energy level / shell. Not electron removed from a higher energy sub-level / orbital. Ignore electron removed from a lower energy sub-level / orbital. Ignore ‘more protons than electrons’. Not ‘greater nuclear charge’. Ignore ‘greater effective nuclear charge’. Ignore shielding. 1 [8]

M21.(a) 5s2 4d10 5p4 / 4d10 5s2 5p4 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p4

Page 59 Seven Kings High School or 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p4 Allow any order but must finish with 5p4 1

(b) (i) or

M1 for top line 1

127.8 M2 for correct denominator 1 127.8 with no working shown scores 3 marks 1

1 Mark for 100 dependent on top line correct 1

127.8 1

(ii) Other isotopes present / some isotopes absent / different abundances of isotopes 1

(d) 128 Only 1

Most abundant ion (QoL − superlative) M2 dependent on correct M1 1

(e) 2+ ion formed / 2 electrons removed Due to 128Te2+ = 2 marks

Page 60 Seven Kings High School 1

From 128 (Te) Mark independently 1

(f) Same If not same CE = 0 / 2 1

(Each isotope has the) same number of protons / same nuclear charge and same number of electrons / electronic configuration Ignore more neutrons in 130Te 1 [12]

+ M22.(a) [CH3OCOCOOH] Allow names 1

+ [CH3OCOCOOCH3] Do not allow molecular formula 1

(b) Positive ions are accelerated by an electric field 1

To a constant kinetic energy 1

The positive ions with m / z of 104 have the same kinetic energy as those with m / z of 118 and move faster 1

Therefore, ions with m / z of 104 arrive at the detector first 1 [6]

Page 61 Seven Kings High School

M23.D [1]

M24.(a) (Ions accelerated by) attraction to negatively charged plate /electric field Mark independently 1

Ions detected by gaining electrons Allow the transfer of electrons 1

Abundance determined by (size) of current flowing (or amount of electrons gained) in the detector Allow current is proportional to abundance 1

(b) Mass =

Mass = 8.6(4) × 10−26 1

V = 1.71 × 106 ms−1 Allow ecf from (b) (note if 8.6 × 10−23 in (b) leads to approx. 5.4 × 104 ms−1) 1

(d) Sketch with peaks at 158, 160, 162 Mark independently 1

In ratio 25%:50%:25% Allow approx. ratio 1:2:1 1

Page 62 Seven Kings High School (e) % abundance mXe = 20(%) Working must be shown 1

131.31 = (0.28*129) + (0.25*131) + (0.27*132) + (0.20*m) 1

131.31 – 104.51 = 0.2m 1

Mass number = 134 Answer must be an integer 1 [12]

M25.D [1]

M26.C [1]

M27.(a) 1s22s22p63s23p1 1

1s22s22p63s23p63d3 1 If noble gas core used correctly in both then scores 1 Allow subscripts and capitals Ignore 4s0

(b) Sr2+ Ignore name and correct proton/mass number Allow Sr+2 1

Page 63

Name: ______Nomenclature exam pack

Class: ______

Date: ______

Time: 240 minutes

Marks: 225 marks

At minimum please complete questions: Q1 (3 marks) Q6 (5 marks) Comments: Q12 a-c (8 marks) Q14a (1 marks) Q18a (1 marks) Q19 (8 marks) Q22 (10 marks)

Page 1 of 64 Q1. This question is about the structures of some organic molecules.

(a) Draw the skeletal formula of 3-methylbutanal.

(1)

(b) Draw the displayed formula of C5H11Br that is the major product of the reaction of 2- methylbut-2-ene with hydrogen bromide.

(1)

(c) Thermal cracking of hydrocarbons produces molecules that are attacked by electrophiles because they have a region of high electron density.

Draw the structure of one of these molecules that contains four carbon atoms.

(1) (Total 3 marks)

Q2. Which compound is a structural isomer of Z-but-2-ene?

A butane

B E-but-2-ene

Page 2 of 64 C cyclobutane

D methylbut-2-ene (Total 1 mark)

Q3. How many structural isomers are there with the molecular formula C3H6BrCl?

A 4

B 5

C 6

D 7 (Total 1 mark)

Q4. In concentrated alkali, propanone reacts with hydroxide ions to form an equilibrium mixture as shown.

Which curly arrow does not appear in the mechanism of this reaction?

(Total 1 mark)

Q5. Which compound does not show stereoisomerism?

A 1,2-dichloropropene

Page 3 of 64 B 1,2-dichloropropane

C 1,3-dichloropropene

D 1,3-dichloropropane (Total 1 mark)

Q6. Avgas is an aviation fuel used in the internal combustion engines of helicopters. It consists of a large number of hydrocarbons, including a high proportion of hexane, which can exist as several isomers.

(a) Draw the skeletal formulae of two branched isomers of hexane.

(1)

(b) State the type of isomerism shown by these branched isomers.

______(1)

(c) Safety signs on the fuselage of the helicopter state that the air inlets to the engine need to be cleaned out regularly.

Write an equation for the combustion of hexane that would happen in the helicopter engine if the air inlets were partially blocked with debris.

______(2)

(d) Suggest how this partial blockage might affect the performance of the helicopter engine.

______

______(1) (Total 5 marks)

Q7. What is the total number of structural isomers with the molecular formula C2HBrClF3?

Page 4 of 64 A 2

B 3

C 4

D 5 (Total 1 mark)

Q8. Which is a pair of functional group isomers?

(Total 1 mark)

Q9. Z-Retinal, shown in the diagram, is a component in vitamin A.

Which of the double bonds, labelled A, B, C or D, is responsible for the letter Z in the name?

Page 5 of 64

D (Total 1 mark)

Q10. This question is about isomerism.

(a) How many isomers are represented by the formula C5H12?

Tick (✔) one box.

(b) Name the type of structural isomerism shown by the isomers of C5H12

______(1)

Draw three-dimensional representations of the two enantiomers of 2- hydroxypropanenitrile, showing how the two structures are related to each other.

(2)

Page 6 of 64 (d) Describe how separate samples of each of these enantiomers could be distinguished.

______

______(2)

(e) Butan-2-ol reacts with concentrated sulfuric acid to produce three isomeric alkenes.

Name and outline a mechanism to show how any one of the alkenes is formed.

Explain how this reaction can lead to the formation of each of these three alkenes.

Name of mechanism ______

Mechanism

Explanation ______

______

______(8) (Total 13 marks)

Page 7 of 64 Q11. When methylbenzene reacts with ethanoyl chloride in the presence of aluminium chloride, the product, H, is formed.

(a) Deduce the molecular formula of H.

______(1)

(b) Two other isomers are also produced in the reaction.

Draw the structure of one of the other isomers.

Name the type of structural isomerism shown by these three products.

Structure

Type of isomerism ______(2)

Include an equation for the formation of the reactive intermediate that is involved in the reaction.

Name ______

Equation ______

Mechanism

Page 8 of 64 (5) (Total 8 marks)

Q12. Compound J, known as leaf alcohol, has the structural formula CH3CH2CH=CHCH2CH2OH and is produced in small quantities by many green plants. The E isomer of J is responsible for the smell of freshly cut grass.

(a) Give the structure of the E isomer of J.

(1)

(b) Give the skeletal formula of the organic product formed when J is dehydrated using concentrated sulfuric acid.

(1)

Explain how the Cahn-Ingold-Prelog (CIP) priority rules can be used to deduce the full IUPAC name of this compound.

______

Page 9 of 64 ______

______(6)

(d) The effect of gentle heat on maleic acid is shown below.

A student predicted that the yield of this reaction would be greater than 80%.

In an experiment,10.0 g of maleic acid were heated and 6.53 g of organic product were obtained.

Is the student correct? Justify your answer with a calculation using these data.

______

______(2) (Total 10 marks)

Q13. 2-bromo-2-methylpentane is heated with potassium hydroxide dissolved in ethanol. Two structural isomers are formed.

(a) State the meaning of the term structural isomers.

______

______(1)

(b) Name and draw the mechanism for the formation of one of the isomers.

Name of mechanism ______

Mechanism

Page 10 of 64

(5) (Total 6 marks)

Q14. Isooctane (C8H18) is the common name for the branched-chain hydrocarbon that burns smoothly in car engines. The skeletal formula of isooctane is shown below.

(a) Give the IUPAC name for isooctane.

______(1)

(b) Deduce the number of peaks in the 13C NMR spectrum of isooctane.

8 (1)

(c) Isooctane can be formed, together with propene and ethene, in a reaction in which one molecule of an alkane that contains 20 carbon atoms is cracked.

Using molecular formulas, write an equation for this reaction.

______(1)

(d) How do the products of the reaction in part (c) show that the reaction is an example of thermal cracking?

______(1)

Page 11 of 64 (e) Deduce the number of monochloro isomers formed by isooctane. Draw the structure of the monochloro isomer that exists as a pair of optical isomers.

Number of monochloro isomers ______

Structure

(2)

(f) An isomer of isooctane reacts with chlorine to form only one monochloro compound.

Draw the skeletal formula of this monochloro compound.

(1)

(g) A sample of a monochlorooctane is obtained from a comet. The chlorine in the monochlorooctane contains the isotopes 35Cl and 37Cl in the ratio 1.5 : 1.0 Calculate the Mr of this monochlorooctane.

Mr = ______(2)

(h) Isooctane reacts with an excess of chlorine to form a mixture of chlorinated compounds. One of these compounds contains 24.6% carbon and 2.56% hydrogen by mass. Calculate the molecular formula of this compound.

Page 12 of 64

Molecular formula = ______(3) (Total 12 marks)

Q15. How many isomers have the molecular formula C5H12?

A 2

B 3

C 4

D 5 (Total 1 mark)

Q16. How many structural isomers have the molecular formula C4H9Br?

A 2

B 3

C 4

D 5 (Total 1 mark)

Q17. How many secondary amines have the molecular formula C4H11N?

A 2

B 3

C 4

D 5 (Total 1 mark)

Page 13 of 64 Q18. Octane and isooctane are structural isomers with the molecular formula C8H18. The displayed formulas and boiling points of octane and isooctane are shown in Figure 1.

Figure 1

(a) Give the IUPAC name for isooctane.

______(1)

(b) Octane and isooctane can be separated in the laboratory.

Name a laboratory technique that could be used to separate isooctane from a mixture of octane and isooctane.

Outline how this technique separates isooctane from octane.

Name ______

Outline ______

______

______(3)

(c) Isooctane is added to petrol to increase its octane rating. Some high- performance engines require fuel with a higher octane rating.

Write an equation for the complete combustion of isooctane. Use the molecular formula (C8H18) of isooctane in your equation.

______(1)

Page 14 of 64 (d) Explain, in general terms, how a catalyst works.

______

______(2)

(e) Carbon monoxide is produced when incomplete combustion takes place in engines. Nitrogen monoxide is another pollutant produced in car engines.

Write an equation to show how these pollutants react together in a catalytic converter.

______(1)

(f) Platinum, palladium and rhodium are metals used inside catalytic converters. A very thin layer of the metals is used on a honeycomb ceramic support.

Explain why a thin layer is used in this way.

______

______(2)

(g) Oleic acid (C18H34O2) is a straight-chain fatty acid obtained from plant oils. Isooctane can be made from oleic acid. The skeletal formula of oleic acid is shown in Figure 2.

Figure 2

Identify a reagent that could be used in a chemical test to show that oleic acid is unsaturated.

State what would be observed in this test.

Reagent ______

Observation ______

Page 15 of 64 ______(2) (Total 12 marks)

Q19. The alkene 3-methylpent-2-ene (CH3CH=C(CH3)CH2CH3) reacts with hydrogen bromide to form a mixture of 3-bromo-3-methylpentane and 2-bromo-3-methylpentane.

(a) The alkene 3-methylpent-2-ene (CH3CH=C(CH3)CH2CH3) exists as E and Z stereoisomers.

Draw the structure of Z-3-methylpent-2-ene.

(1)

(b) Name and outline the mechanism for the formation of 3-bromo-3-methylpentane from this reaction of 3-methylpent-2-ene with hydrogen bromide.

Explain why more 3-bromo-3-methylpentane is formed in this reaction than 2-bromo- 3-methylpentane.

______

______(7) (Total 8 marks)

Q20.

Page 16 of 64 An organic compound is found to contain 40.0% carbon, 6.7% hydrogen and 53.3% oxygen.

Which of the following compounds could this be?

A Ethanol

B Ethanoic acid

C Methanol

D Methanoic acid (Total 1 mark)

Q21. The structure of cyclohexene is shown.

Which of the following is the general formula of cyclic alkenes such as cyclohexene?

A CnH2n–4

B CnH2n–2

C CnH2n

D CnH2n+2

(Total 1 mark)

Q22. (a) Octane (C8H18) is an important compound in petrol.

(i) Identify the homologous series to which octane belongs.

______(1)

(ii) Write an equation to show the complete combustion of C8H18

______(1)

(iii) An isomer of octane used to improve the performance of car engines is shown.

Page 17 of 64

Give the IUPAC name of this isomer.

______(1)

(b) Compound X is produced when an alkane is cracked.

(i) Give the IUPAC name for compound X.

______(1)

(ii) One molecule of an alkane is cracked to produce one molecule of compound X, one molecule of octane and one molecule of ethene.

Deduce the molecular formula of this alkane.

______(1)

(iii) Name the type of cracking that produces a high yield of compound X. Give two conditions required for this process.

Type of cracking ______

Conditions ______

______(2)

(iv) Compound X has several isomers. The structure of X is repeated here.

Draw the displayed formula of a chain isomer, a position isomer and a functional group isomer of compound X.

Displayed formula of isomer of Type of isomer compound X

Page 18 of 64 Chain

Position

Functional group

(3) (Total 10 marks)

Q23. Two reactions of 2-bromopentane, (CH3CH2CH2CHBrCH3) are shown.

The C5H10 formed in reaction 1 exists as a mixture of three isomers, one of which is pent- 1-ene. Two of the isomers are a pair of stereoisomers. All three isomers decolourise bromine.

(a) The same reagent is used in both reactions. The product is determined by the choice of conditions.

State the reagent and the conditions for each of reaction 1 and reaction 2.

State the role of the reagent in each reaction.

Name and outline the mechanism of reaction 1 for the formation of pent-1-ene.

______

Page 19 of 64 ______(8)

(b) All three isomers of C5H10 contain the same functional group.

Draw the displayed formula of pent-1-ene.

Draw the structures of the pair of stereoisomers and give their full IUPAC names.

Explain the origin of the stereoisomerism shown.

______

______(5)

Outline a method to compare the rate of hydrolysis of 1-chlorobutane with that of 2- chlorobutane. State how the method would ensure a fair test.

______

Page 20 of 64 ______

______

______(4) (Total 17 marks)

Q24. Central heating fuel, obtained by the fractional distillation of crude oil, contains saturated hydrocarbons with the molecular formula C16H34

(a) Give the meaning of the terms saturated and hydrocarbon as applied to saturated hydrocarbons.

Saturated ______

______

Hydrocarbon ______

______(2)

(b) If the boiler for a central heating system is faulty, a poisonous gas may be produced during the combustion of C16H34

Write an equation for the reaction that forms this poisonous gas and one other product only.

______(1)

(c) Explain why the sulfur compounds found in crude oil should be removed from the fractions before they are used for central heating fuel.

______

______(2)

(d) A hydrocarbon C16H34 can be cracked to form C8H18, ethene and propene.

(i) Write an equation to show this cracking reaction.

Page 21 of 64 ______(1)

(ii) Suggest one important substance manufactured on a large scale from propene.

______(1)

(iii) Draw the displayed formula of the functional group isomer of propene.

(1)

(e) There are many structural isomers with the molecular formula C8H18

Draw the structure of 2,3,3-trimethylpentane.

(1)

(f) A compound C8H18 reacts with chlorine to give several haloalkanes.

Give the IUPAC name of the following haloalkane.

______(1)

Page 22 of 64 (Total 10 marks)

Q25. The carbonyl compound CH3CH2CHO reacts very slowly with HCN

(a) Name and outline a mechanism for the reaction of CH3CH2CHO with HCN

Name of mechanism ______

Mechanism

(5)

(b) The reaction in part (a) produces a pair of enantiomers.

(i) Draw the structure of each enantiomer to show how they are related to each other.

(2)

(ii) State and explain how you could distinguish between the two enantiomers.

______

______(2)

______(1)

(d) In practice, KCN rather than HCN is added to the carbonyl compound.

–10 –3 Given that Ka for HCN = 4.0 × 10 mol dm , suggest why the reaction with HCN is very slow.

______

Page 23 of 64 ______

______

______(2)

(e) Acrylic fibres are used as a substitute for wool. Acrylics are copolymers of acrylonitrile with other compounds.

Acrylonitrile is the common name for the following compound.

H2C = CH − C ≡ N

(i) Acrylonitrile can be formed from propene.

Write an equation for the reaction of propene with ammonia and oxygen to form acrylonitrile and one other product.

______(1)

(ii) The term copolymer is used to describe the product obtained when two or more different monomers form a polymer.

Draw the repeating unit of the acrylic copolymer that contains 75% acrylonitrile monomer and 25% chloroethene monomer.

(1)

(iii) Name the type of polymerisation involved in part (ii)

______(1) (Total 15 marks)

Q26. (a) The hydrocarbon but-1-ene (C4H8) is a member of the homologous series of alkenes. But-1-ene has structural isomers.

(i) State the meaning of the term structural isomers.

______

Page 24 of 64 (2)

(ii) Give the IUPAC name of the position isomer of but-1-ene.

______(1)

(iii) Give the IUPAC name of the chain isomer of but-1-ene.

______(1)

(iv) Draw the displayed formula of a functional group isomer of but-1-ene. (1)

(b) But-1-ene burns in a limited supply of air to produce a solid and water only.

(i) Write an equation for this reaction.

______(1)

(ii) State one hazard associated with the solid product in part (b)(i).

______(1)

(c) One mole of compound Y is cracked to produce two moles of ethene, one mole of but-1-ene and one mole of octane (C8H18) only.

(i) Deduce the molecular formula of Y.

______(1)

(ii) Other than cracking, give one common use of Y.

______(1)

(d) In cars fitted with catalytic converters, unburned octane reacts with nitrogen monoxide to form carbon dioxide, water and nitrogen only.

(i) Write an equation for this reaction.

______(1)

(ii) Identify a catalyst used in a catalytic converter.

______(1) (Total 11 marks)

Q27.

Page 25 of 64 (a) The structure of the bromoalkane Z is

Give the IUPAC name for Z.

Give the general formula of the homologous series of straight-chain bromoalkanes that contains one bromine atom per molecule.

Suggest one reason why 1-bromohexane has a higher boiling point than Z.

______

(Extra space) ______

______

______(3)

(b) Draw the displayed formula of 1,2-dichloro-2-methylpropane.

State its empirical formula.

______

______(2) (Total 5 marks)

Q28. The table below shows the structures of three isomers with the molecular formula C5H10O

Page 26 of 64 Isomer 1

(E)-pent-3-en-2-ol

Isomer 2

pentanal

Isomer 3

(a) Complete the table by naming Isomer 3. (1)

(b) State the type of structural isomerism shown by these three isomers.

______(1)

(i) Draw the structure of (Z)-pent-3-en-2-ol.

(1)

(ii) Identify the feature of the double bond in (E)-pent-3-en-2-ol and that in (Z)-pent-3-en-2-ol that causes these two compounds to be stereoisomers.

______(1)

(d) A chemical test can be used to distinguish between separate samples of Isomer 2 and Isomer 3. Identify a suitable reagent for the test. State what you would observe with Isomer 2 and with Isomer 3.

Page 27 of 64 Test reagent ______

Observation with Isomer 2 ______

______

Observation with Isomer 3 ______

______(3)

(e) The following is the infrared spectrum of one of the isomers 1, 2 or 3.

(i) Deduce which of the isomers (1, 2 or 3) would give this infrared spectrum. You may find it helpful to refer to Table 1 on the Data Sheet.

______(1)

(ii) Identify two features of the infrared spectrum that support your deduction. In each case, identify the functional group responsible.

Feature 1 and functional group ______

______

Feature 2 and functional group ______

______

Page 28 of 64 (2) (Total 10 marks)

Q29. Octane is the eighth member of the alkane homologous series.

(a) State two characteristics of a homologous series.

______

______(2)

(b) Name a process used to separate octane from a mixture containing several different alkanes.

______

______(1)

Give the meaning of the term structural isomerism. Name this isomer and state its empirical formula.

______

______(4)

(d) Suggest why the branched chain isomer shown above has a lower boiling point than octane.

______

Page 29 of 64 ______

______(2) (Total 9 marks)

Q30. There are seven isomeric carbonyl compounds with the molecular formula C5H10O. The structures and names of some of these isomers are given below.

Structure Name

pentanal

2-methybutanal

2, 2-dimethypropanal

pentan-2-one

(a) (i) Complete the table.

(ii) Two other isomeric carbonyl compounds with the molecular formula C5H10O are not shown in the table. One is an aldehyde and one is a ketone. Draw the structure of each.

isomeric aldehyde isomeric ketone

Page 30 of 64

(4)

(b) Pentanal, CH3CH2CH2CH2CHO, can be oxidised to a carboxylic acid.

(i) Write an equation for this reaction. Use [O] to represent the oxidising agent.

______

(ii) Name the carboxylic acid formed in this reaction.

______(2)

(i) Identify this alcohol.

______

(ii) State the class to which this alcohol belongs.

______(2) (Total 8 marks)

Q31. Hexane is a member of the homologous series of alkanes.

(a) State two characteristics of a homologous series.

Characteristic 1 ______

______

Characteristic 2 ______

______(2)

(b) (i) Hexane can be converted into 2,2-dichlorohexane.

Draw the displayed formula of 2,2-dichlorohexane and deduce its empirical formula.

Displayed formula

Page 31 of 64 Empirical formula ______

______(2)

(ii) Explain why 2,2-dichloro-3-methylpentane is a structural isomer of 2,2- dichlorohexane.

______

______(2)

C6H14 + 2Cl2 → C6H12Cl2 + 2HCl

Calculate the percentage atom economy for the formation of C6H12Cl2 in this reaction.

______

______(2)

(d) The boiling points of some straight-chain alkanes are shown below.

Alkane C4H10 C5H12 C6H14

Boiling point / °C – 0.5 36.3 68.7

(i) Explain the trend in these boiling points.

______

______(2)

(ii) Name a process which can be used to separate C5H12 from C6H14

______(1) (Total 11 marks)

Q32. The reaction of bromine with ethane is similar to that of chlorine with ethane. Three steps in the bromination of ethane are shown below.

• Step 1 Br2 2Br

• • Step 2 Br + CH3CH3 CH3CH2 + HBr

Page 32 of 64 • • Step 3 CH3CH2 + Br2 CH3CH2Br + Br

(a) (i) Name this type of mechanism.

______

(ii) Suggest an essential condition for this reaction.

______

(iii) Steps 2 and 3 are of the same type. Name this type of step.

______

(iv) In this mechanism, another type of step occurs in which free-radicals combine. Name this type of step. Write an equation to illustrate this step.

Type of step ______

Equation______(5)

(b) Further substitution in the reaction of bromine with ethane produces a mixture of liquid organic compounds.

(i) Name a technique which could be used to separate the different compounds in this mixture.

______

(ii) Write an equation for the reaction between bromine and ethane which produces hexabromoethane, C2Br6, by this substitution reaction.

______(2)

(c) The compound 1,2-dibromo-1,1,2,2-tetrafluoroethane is used in some fire extinguishers. Draw the structure of this compound.

(1)

(d) Halothane is used as an anaesthetic and has the following structure.

(i) Give the systematic name of halothane.

Page 33 of 64 ______

(ii) Calculate the Mr of halothane.

______

(iii) Calculate the percentage by mass of fluorine in halothane.

______(3) (Total 11 marks)

Q33. (a) The infra-red spectrum of compound A, C3H6O2, is shown below.

Identify the functional groups which cause the absorptions labelled X and Y.

Using this information draw the structures of the three possible structural isomers for A.

Label as A the structure which represents a pair of optical isomers. (6)

(b) Draw the structures of the three branched-chain alkenes with molecular formula C5H10

Draw the structures of the three dibromoalkanes, C5H10Br2, formed when these three alkenes react with bromine.

One of these dibromoalkanes has only three peaks in its proton n.m.r. spectrum. Deduce the integration ratio and the splitting patterns of these three peaks. (10) (Total 16 marks)

Q34. Which one of the following can exhibit both geometrical and optical isomerism?

Page 34 of 64 A (CH3)2C=CHCH(CH3)CH2CH3

B CH3CH2CH=CHCH(CH3)CH2CH3

C (CH3)2C=C(CH2CH3)2

D CH3CH2CH(CH3)CH(CH3)C=CH2 (Total 1 mark)

Q35. How many different alkenes are formed when 2-bromo-3-methylbutane reacts with ethanolic potassium hydroxide?

A 2

B 3

C 4

D 5 (Total 1 mark)

Page 35 of 64 Mark schemes

Q1. (a)

Must be a skeletal structure 1

(b)

Must be a displayed structure 1

but-1-ene or but-2-ene or methylpropene

allow butadiene 1 [3]

Q2. C [1]

Q3. B [1]

Q4. B [1]

Q5. D

Page 36 of 64 [1]

Q6. (a) Any two of these isomers

(b) Chain isomerism Mark consequential to part (a) 1

C6H14 + 3.5O2 6C + 7H2O

Allow equations containing CO2 as long as either C, CO or both are also present 1

(d) Less energy given out by the fuel / engine is less powerful / less efficient / needs to burn more fuel to get the same energy / increased costs due to need to use more fuel Do not allow answers linked to CO poisoning or incomplete combustion 1 [5]

Q7. C [1]

Q8. A [1]

Q9.

Page 37 of 64 C [1]

Q10. (a) 3 1

(b) Chain. 1

(c)

One 3D enantiomer. 1 Second enantiomer correctly drawn as 3D mirror image of first. 1

(d) Plane-polarised light. 1

Rotated in opposite directions. 1

(e) Elimination

Page 38 of 64

Extended response question

Mechanism (3 marks)

M2 arrow from lone pair on O to H+

st + M3 1 intermediate and arrow from C–O H2 bond to O (with loss of H2O)

M4 2nd intermediate (carbocation) and arrow from C–H bond to C–C (with loss of H+) to form C=C

M3 and M4 can be scored in one step (see alternative mechanism below).

If carbocation incorrect then answer cannot score maximum marks.

Explanation of formation of 3 alkenes

M5 loss of H+ from C (in carbocation) adjacent to +C (to which −OH was attached)

M6 From 1C−2C+–3C–4C leads to but-1-ene

M7 From 1C–2C+–3C–4C leads to but-2-ene

M8 But-2-ene formed as mixture of E-Z isomers 8

Page 39 of 64 Alternative mechanism

[14]

Q11. (a) C9H10O 1

(b)

Position (isomerism). Allow Positional. 1

+ − CH3COCl + AlCl3 CH3CO + AlCl4 1 ⟶

Page 40 of 64

Mechanism 3 marks: + M1 arrow from circle or within it to C of CH3C O (+ must be + on C of CH3C O). 1 M2 for Intermediate (must be 4-isomer) CH3CO must be correctly positioned and bonded to gain M2 horseshoe must not extend beyond C2 to C6 but can be smaller + not too close to C1. 1 M3 arrow into hexagon unless Kekule Loss of H+ (allow from incorrect isomer) Allow M3 arrow independent of M2 structure Ignore base removing H in M3. Allow Kekule structures (which must be correct). 1 [8]

Q12. (a)

(b) 1

(c) Stage 1: consider the groups joined to right hand carbon of the C=C bond Extended response Maximum of 5 marks for answers which do not show a sustained line of reasoning which is coherent, relevant, substantiated and logically structured.

Consider the atomic number of the atoms attached M1 can be scored in stage 1 or stage 2 1

Page 41 of 64 C has a higher atomic number than H, so CH2OH takes priority 1

Stage 2: consider the groups joined to LH carbon of the C=C bond

Both groups contain C atoms, so consider atoms one bond further away 1

C, (H and H) from ethyl group has higher atomic number than H, (H and H) from methyl group, so ethyl takes priority 1

Stage 3: conclusion

The highest priority groups, ethyl and CH2OH are on same side of the C=C bond so the isomer is Z Allow M5 for correct ECF conclusion using either or both wrong priorities deduced in stages 1 and 2 1

The rest of the IUPAC name is 3-methylpent-2-en-1-ol 1

(d) Moles of maleic acid = 10.0 / 116.0 = 8.62 × 10–2

AND mass of organic product expected = (8.62 × 10–2) × 98.0 = 8.45 g

Or moles of organic product formed = 6.53 / 98.0 = 6.66 × 10–2 1

% yield = 100 × 6.53 / 8.45

OR = 100 × (6.66 × 10–2) / (8.62 × 10–2)

= 77.294 = 77.3%

AND statement that the student was NOT correct 1 [10]

Q13. (a) (Compounds with the) same molecular formula but different structural / displayed / skeletal formula 1

(b) (basic) elimination 1

Mechanism points:

Correct arrow from lone pair on :OH– to H on C adjacent to C–Br 1

Correct arrow from C–H bond to C–C 1

Correct arrow from C–Br bond to Br 1

Page 42 of 64 Structure of chosen product 1

[6]

Q14. (a) 2,2,4-trimethylpentane 1

(b) 5 1

(d) Mainly alkenes formed 1

(e) 4 (monochloro isomers) 1

(f)

35 (g) C8H17 Cl = 96.0 + 17.0 + 35.0 = 148.0 37 and C8H17 Cl = 96.0 + 17.0 + 37.0 = 150.0 Both required

Page 43 of 64 1

Mr of this C8H17Cl = 148.8 1

(h) = 2.05 : 2.56 : 2.05

Simplest ratio =

= 1 : 1.25 : 1 1

Whole number ratio (× 4) = 4 : 5 : 4 1

MF = C8H10Cl8 1 [12]

Q15. B [1]

Q16. C [1]

Q17. B [1]

Q18. (a) 2,2,4-trimethylpentane This answer only but ignore punctuation 1

(b) M1 (fractional or simple) distillation Incorrect process in M1 CE=0 If M1 blank, mark on for M2 and M3 (ignore boiling, condensing) 1

M2 idea that isooctane / the one with the lower boiling point boils (first) (or reaches top of column first) Ignore reference to octane boiling and being collected at higher temperature If temperature referred to, should be between 99 and 124°C “it” refers to isooctane

Page 44 of 64 M2 – allow vaporises/evaporates first 1

M3 idea that isooctane condenses / liquefies and collected Penalise M2 and M3 if octane boils first In M2 and M3 – if no specific reference to individual alkanes, could score one mark for M2 + M3 combined if M2 and M3 both otherwise correct M2 and M3 must refer to a laboratory apparatus (not to an industrial process) 1

(c) C8H18 + 12½O2 → 8CO2 + 9H2O Accept multiples; ignore state symbols Accept any correct structural representation of isooctane 1

(d) M1 Alternative route/mechanism/pathway 1

M2 With lower activation energy

Accept Ea for activation energy 1

(e) 2CO + 2NO → 2CO2 + N2 Accept multiples; ignore state symbols 1

(f) M1 to reduce amount of metals needed / small amount of metal needed Relates to low amount of metal 1

M2 Increase / maximise / produce large surface area or to give catalyst a larger surface area: volume ratio or so that high(er) proportion of atoms/metal is on surface Is related to large surface area 1

(g) M1 bromine (water or in organic solvent or CCl4) / Br2 (aq) / Br2 No reagent or an incorrect reagent (e.g. bromide), CE=0; Penalise Br (or incorrect formula of other correct reagent) but mark on for M2 It must be a whole reagent and/or correct formula If oxidation state given in name, it must be correct If ‘manganate’ or ‘manganate(IV)’ or incorrect formula, penalise M1 but mark on Ignore ‘acidified’ 1

M2 (orange/yellow to) colourless / decolourised / loses its colour Ignore goes clear Ignore brown/red, but penalise other incorrect colours 1 Alternatives:

Page 45 of 64 M1 = potassium manganate(VII), M2 = colourless M1 = conc sulfuric acid, M2 = brown M1 = iodine, M2 = colourless [12]

Q19.

(a) Must show all 4 groups bonded to C=C

Allow CH3− for methyl group; allow C2H5 for ethyl group Allow correct structure of the style

Allow correct skeletal structure

(b) M1 electrophilic addition

NB the arrows here are double-headed 1

M2 must show an arrow from the double bond towards the H atom of the H-Br molecule 1

M3 must show the breaking of the H-Br bond 1

M4 is for the structure of the tertiary carbocation 1

M5 must show an arrow from the lone pair of electrons on the negatively charged bromide ion towards the positively charged atom (of either a secondary or) of a

Page 46 of 64 tertiary carbocation 1

M6 3-bromo-3-methylpentane is formed from 3y carbocation OR 2-bromo-3-methylpentane is formed from 2y carbocation 1

M7 3y carbocation more stable than 2y 1 M2-M5 Penalise one mark from their total if half-headed arrows are used M2 Ignore partial negative charge on the double bond M3 Penalise incorrect partial charges on H-Br bond and penalise formal charges Penalise M4 if there is a bond drawn to the positive charge Penalise only once in any part of the mechanism for a line and two dots to show a bond Max 3 of any 4 marks (M2-5) for wrong organic reactant or wrong organic product (if shown) or secondary carbocation Max 2 of any 4 marks in the mechanism for use of bromine Do not penalise the “correct” use of “sticks” For M5, credit attack on a partially positively charged carbocation structure but penalise M4 M6 is high demand and must refer to product being formed from/via correct class of carbocation M7 is high demand and must be clear answer refers to stability of carbocations (intermediates) not products Candidate that states that products are carbocations would lose M6 and M7 M6,7 allow carbonium ion in place of carbocation; or a description of carbocation in terms of alkyl groups/ number of carbon atoms joined to a positive C

When asked to outline a mechanism, candidates are expected to draw a mechanism with curly arrows (specification 3.3.1.2). On this occasion only we would allow a detailed description as shown. M2 must describe the movement of a pair of electrons / curly arrow from the C=C towards the H atom of the H-Br molecule M3 must describe the breaking of the H-Br bond with the bonding pair of electrons moving to the Br / curly arrow from H-Br bond to Br M4 is for the structure of the tertiary carbocation (i.e. positive C bonded to one methyl and two ethyl groups) M5 must describe the movement of a pair of electrons from the Br− ion to the positive C atom of the carbocation / curly arrow from the lone pair of electrons on the negatively charged bromide ion towards the positively charged C atom (of either a secondary or) of a tertiary carbocation [8]

Page 47 of 64 Q20. B [1]

Q21. B [1]

Q22. (a) (i) Alkane(s)

Ignore CnH2n+2 1

(ii) C8H18 + 12.5O2 → 8CO2 + 9H2O Allow multiples 1

(iii) 2, 2, 4-trimethylpentane 1

(b) (i) But-1-ene Ignore (E or Z) 1

(ii) C14H30 1

(iii) Thermal If catalytic CE = 0 1

High pressure / 7000kPa / 70 atms and High temperature/temperature in range 400-1000°C (673–1273K) (Allow ≥1000 kPa or ≥10 atms – no upper value) Allow high temperature and pressure or high pressure and temperature If no units for temperature allow 673-1000 Must show unambiguous structure Penalise lack of displayed formula once only 1

(iv) 1

Page 48 of 64

1 [10]

Q23. (a) NaOH/KOH IGNORE OH- NOT M1 if any mention of acidified/H+ in reagents or conditions 1

Reaction 1 = ethanolic/alcoholic AND reaction 2 = aqueous IGNORE temp NOT ethanoic 1

rxn 1 = base/proton acceptor 1

rxn 2 = nucleophile/lone pair donor/electron pair donor 1

(Base) Elimination NOT nucleophilic 1

M6 must show an arrow from the lone pair on the oxygen of a negatively charged hydroxide ion to a correct H atom

Page 49 of 64 M8 is independent provided it is from their original molecule and shows curly arrow from C-Br to Br ALLOW correct E1 mechanism IGNORE incorrect inorganic products If forming pent-2-ene can award M8 only even if arrows in mechanism correct If C chain length or halogen wrong in reactant or product max 2/3 1 1 1

(b) 1

1 If no M2 and M3 ALLOW 1 mark if both structures OR both names correct NOT cis and trans

No free rotation around C=C ALLOW no rotation of C=C 1

2 different atoms/groups on each of the C=C Cs owtte IGNORE ‘functional’ 1

(c) Same volume/amount of AgNO3(aq) added to same volume/amount/no. of drops of haloalkane (in beaker/flask) in each experiment Both volume references needed IGNORE inappropriate volumes 1

Same temp OR same [AgNO3] each time 1

Page 50 of 64 record time to measure sensible observation about the amount of AgCl ppt e.g. first appearance of ppt / ppt obscures mark / reading on a colorimeter IGNORE colour of ppt ALLOW silver mirror NOT reference to same time if describing method based on timing how long (for ppt to form) ALLOW gravimetric method based on same time for each experiment 1

Rate = amount/time OR proportional to 1/time OR reference to shorter time = higher rate/longer time = lower rate ALLOW greater mass = higher rate if gravimetric method 1 [17]

Q24. (a) Saturated − single bonds only / no double bonds 1

Hydrocarbon − contains carbon and hydrogen (atoms) only 1

(b) C16H34 + 16.5O2 16CO + 17H2O Allow multiples 1

Allow equation to produce SO2. Ignore sulfur oxides. 1

Which causes acid rain If formula shown it must be correct M2 is dependent on M1. But if M1 is sulfur oxides, allow M2.

For M2 allow consequence of acid rain or SO2. Ignore greenhouse effect and toxic 1

(d) (i) C16H34 C8H18 + C2H4 + 2C3H6 Allow multiples 1

(ii) polypropene / propan(-1 or 2-)ol / propane(-1,2-)diol / isopropanol / propanone / propanal Accept alternative names Ignore plastic and polymer 1

(iii)

Page 51 of 64

(e)

Allow any unambiguous representation 1

(f) 2,4-dichloro-2,4-dimethylhexane Only but ignore punctuation 1 [10]

Q25. (a) Nucleophilic addition 1

M4 for lp, arrow and H+

Allow C2H5− for CH3CH2− • M1 and M4 include lone pair and curly arrow. • Allow: CN− but arrow must start at lone pair on C. • M2 not allowed independent of M1, but allow M1 for correct attack on C+. • + rather than δ+ on C=O loses M2. • Penalise incorrect partial charges. • M3 is for correct structure including minus sign but lone pair is part of M4. • Penalise extra curly arrows in M4. 4

Page 52 of 64 (b) (i) M1

M1 for correct structure of product of part (a).

Allow C2H5− for CH3CH2−.

Penalise wrongly bonded, OH or CN or CH2CH3 once only in clip. 1

M2 cannot be gained by simply swapping two or more groups with no attempt to show a mirror image., e.g. do not allow M2 for

because these do not show the enantiomers as mirror images.

Students must show an attempt at mirror images, eg allow

ie vertical groups same and horizontal swapped as if there was a mirror between them

No mirror need be shown

Do not penalize wedge bond when wedge comes into contact with both C & N However these two could score M2 if placed as below as if with a “mirror” horizontally between them.

(ii) M1 (Plane) polarized light M2 only scores following correct M1

Page 53 of 64 1

M2 Rotated in opposite directions (equally) (only allow if M1 correct or close) Not just in different directions but allow one rotates light to the left and one to the right. Not molecules rotate. 1

(d) Weak acid / (acid) only slightly / partially dissociated / ionised Ignore rate of dissociation. 1

[CN−] very low Allow (very) few cyanide ions. Mark independently. 1

(e) (i) H2C=CH−CH3 + NH3 + O2 H2C=CH−CN + 3H2O

H2C=CH−CH3 + NH3 + 3O2 H2C=CH−CN + 3H2O2 OR doubled.

Allow C3H6 and CH2CHCN or C3H3N on this occasion only. 1

(ii)

Ignore n. Must show trailing bonds. Do not penalise C–NC bond here on this occasion.

Must contain, in any order,

3 of

Allow

and one of

Page 54 of 64 Allow –CH2CH(CN)CH2CHCl− etc. 1

(iii) Addition (polymerization) Allow self-addition. Do not allow additional. 1 [15]

Q26. (a) (i) (Compounds with the) same molecular formula Allow same number and type of atom for M1 Ignore same general formula. 1

But different structural formula / different displayed formula / different structures / different skeletal formula M2 dependent on M1 Not different positions of atoms / bonds in space. 1

(ii) But-2-ene Allow but-2-ene. Allow but 2 ene. Ignore punctuation. 1

(iii) (2)-methylprop-(1)-ene Do not allow 2-methyleprop-1-ene. 1

(iv)

Do not allow skeletal formulae. Penalise missing H and missing C 1

(b) (i) C4H8 + 2O2 → 4C + 4H2O Accept multiples. 1

Page 55 of 64 (ii) Exacerbates asthma / breathing problems / damages lungs / smog / smoke / global dimming Ignore toxic / pollutant / soot / carcinogen. Do not allow greenhouse effect / global warming / acid rain / ozone. 1

Allow H34C16 C and H must be upper case. 1

(ii) Jet fuel / diesel / (motor) fuel / lubricant / petrochemicals / kerosene / paraffin / central heating fuel / fuel oil Ignore oil alone. Not petrol / bitumen / wax / LPG / camping fuel. 1

(d) (i) C8H18 + 25NO → 8CO2 + 12.5 N2 + 9H2O Accept multiples. 1

(ii) Ir / iridium

Pt / platinum

Pd / palladium

Rh / rhodium 1 [11]

Q27. (a) 2-bromo-2,3-dimethylbutane Ignore punctuation. 1

CnH2n+1Br or CnH 2n+1X or CxH2x+1Br Any order. 1

Stronger / more vdw (forces) between molecules (of 1-bromohexane) QoL Allow converse arguments for Z Not just more IMF. Ignore size of molecule. 1

(b)

Page 56 of 64

C2H4Cl Any order 1 [5]

Q28. (a) Pentan-2-one ONLY but ignore absence of hyphens 1

(b) Functional group (isomerism) Both words needed 1

Award credit provided it is obvious that the candidate is drawing the Z / cis isomer

The group needs to be CHOHCH3 but do not penalise poor C–C bonds or absence of brackets around OH Trigonal planar structure not essential 1

(ii) Restricted rotation (about the C=C)

No (free) rotation (about the C=C) 1

(d) M1 Tollens’ (reagent) M1 Fehling’s (solution) / Benedict’s

2+ (Credit ammoniacal silver nitrate (Penalise Cu (aq) or CuSO4 but OR a description of making mark M2 and M3) Tollens’)

Page 57 of 64 + (Do not credit Ag , AgNO3 or + [Ag(NH3)2 ] or “the silver mirror test” on their own, but mark M2 and M3)

M2 silver mirror M2 Red solid/precipitate

OR black solid or black precipitate (Credit orange or brown solid)

M3 (stays) colourless M3 (stays) blue

OR OR

no (observed) change / no reaction no (observed) change / no reaction

If M1 is blank CE = 0, for the clip Check the partial reagents listed and if M1 has a totally incorrect reagent, CE = 0 for the clip Allow the following alternatives M1 (acidified) potassium dichromate(VI) (solution); mark on from incomplete formulae or incorrect oxidation state M2 (turns) green M3 (stays) orange / no (observed) change / no reaction OR M1 (acidified) potassium manganate(VII) (solution); mark on from incomplete formulae or incorrect oxidation state M2 (turns) colourless M3 (stays) purple / no (observed) change / no reaction In all cases for M3 Ignore “nothing (happens)” Ignore “no observation” 3

(e) (i) Spectrum is for Isomer 1

or named or correctly identified The explanation marks in (e)(ii) depend on correctly identifying Isomer 1. The identification should be unambiguous but candidates should not be penalised for an imperfect or incomplete name. They may say “the alcohol” or the “alkene” or the “E isomer” 1

(ii) If Isomer 1 is correctly identified, award any two from

• (Strong / broad) absorption / peak in the range 3230 to 3550 cm–1 or specified value in this range or marked correctly on spectrum and (characteristic absorption / peak for) OH group /alcohol group

Page 58 of 64 • No absorption / peak in range 1680 to 1750 cm–1 or absence marked correctly on spectrum and (No absorption / peak for a) C=O group / carbonyl group / carbon- oxygen double bond

• Absorption / peak in the range 1620 to 1680 cm–1 or specified value in this range or marked correctly on spectrum and

(characteristic absorption / peak for) C=C group / alkene / carbon-carbon double bond If 6(e)(i) is incorrect or blank, CE=0 Allow the words “dip” OR “spike” OR “trough” OR “low transmittance” as alternatives for absorption. Ignore reference to other absorptions e.g. C-H, C-O 2 [10]

Q29. (a) • (Same) General formula/allow a named homologous series with its general formula

• Chemically similar/same (chemical) reactions

• Same functional group

• Trend in physical properties/eg inc bp as Mr increases

• (Molecules) increase by CH2/Mr = 14 Any two points 2

(b) Fractional distillation/fractionation/chromatography Allow GLC 1

(c) (Molecules/compounds/substances) with the same molecular formula/same number and type of atoms Allow alkanes with same molecular formula Allow same chemical formula in M1 = 0 but can allow M2 1

but different structural formula/different displayed formula/different arrangement of atoms/different structures Not different positions in space 1

2,4-dimethylhexane M2 dependent on M1 1

C4H9 Ignore the absence of dash and/or commas

Page 59 of 64 1

(d) less surface contact/less surface area/less polarisable molecule 1

so fewer/weaker/less Van der Waals’/vdw forces Allow more spherical or fewer points of contact Not smaller molecule/not more compact molecule/not shorter chain Allow converse arguments Must be comparative answer ie not just few VDW forces QoL Assume ‘it’ refers to the branched isomer 1 [9]

Q30. (a) (i) M1 pentan-3-one only 1

M2 CH3CH2CH2COCH3 (insist on C=O being drawn out)

(penalise use of C3H7) 1

(ii) aldehyde (CH3)2CHCH2CHO 1

ketone (CH3)2CHCOCH3 1 (insist on a clear structure for the C=O of the functional groups, but do not be too harsh on the vertical bonds between carbon atom son this occasion) (If both structures correct, but wrong way around, award one mark) (ignore names)

(b) (i) CH3CH2CH2CH2CHO + [O] → CH3CH2CH2CH2COOH

(accept C4H9CHO going to C4H9COOH) (insist on a balanced equation – for example do not credit [O] over the arrow alone) 1

(ii) pentanoic acid (credit pentan–1–oic acid) 1

(c) (i) CH3CH2CH2CH2CH2OH OR pentan–1–ol (If both a structure and a formula are given, credit either correct one of these provided the other is a good, if imperfect, attempt) 1

Page 60 of 64 (ii) Primary (credit 1o or 1) 1 [8]

Q31. (a) General formula;

Chemically similar;

Same functional group;

Trend in physical properties eg inc bp as Mr increases;

Contains an additional CH2 group; Any two points. 2 max

(b) (i)

All bonds and atoms must be shown. 1

C3H6Cl; Allow any order of elements. Do not allow EF consequential on their wrong displayed formula. 1

(ii) Same Molecular formula/ both C6H12Cl2/ same number and type of atoms; 1

Different structural formula/ different structure/ different displayed formula; Not atoms or elements with same MF CE=O. Allow different C skeleton. If same chemical formula can allow M2 only. M2 insufficient to say atoms arranged differently. M2 consequential on M1. 1

= 67.98%; Allow 67.98 or 68.0 or 68%. 1

(d) (i) Bp increases with increasing (molecular) size/ increasing Mr/ increasing no of electrons/increasing chain length;

Page 61 of 64 Atoms CE =0. 1

Increased VDW forces (between molecules) (when larger molecule)/ bigger IMFs; QWC Not dipole-dipole or hydrogen bonds. If VDW between atoms in M2 CE = 0. 1

(ii) Fractional distillation/ fractionation/ GLC/chromatography; 1 [11]

Q32. (a) (i) (free–)radical substitution (both words required for the mark) 1

(ii) uv light OR sunlight OR high temperature OR 150 °C to 500 °C 1

(iii) Propagation (ignore “chain”, “first”, “second” in front of the word propagation) 1

(iv) Termination 1

•CH2CH3 + Br• CH3CH2Br OR 2•CH2CH3 C4H10

(penalise if radical dot is obviously on CH3, but not otherwise)

(penalise C2H5•)

(credit 2Br• Br2) (ignore “chain” in front of the word termination) 1

(b) (i) Fractional distillation OR fractionation (credit gas–liquid chromatography, GLC) 1

(ii) CH3CH3 + 6Br2 C2Br6 + 6HBr

(credit C2H6 for ethane) 1

(d) (i) 2–bromo–2–chloro–1,1,1–trifluoroethane OR 1–bromo–1–chloro–2,2,2–trifluoroethane (insist on all numbers, but do not penalise failure to use alphabet) (accept “flourine” and “cloro” in this instance) 1

Page 62 of 64 (ii) 197.4 only (ignore units) 1

(iii) (57/197.4 × 100) = 28.9% OR 28.88% (credit the correct answer independently in part (d)(iii), even if (d)(ii) is blank or incorrectly calculated, but mark consequential on part (d)(ii), if part (d)(ii) is incorrectly calculated, accepting answers to 3sf or 4sf only) (penalise 29% if it appears alone, but not if it follows a correct answer) (do not insist on the % sign being given) (the percentage sign is not essential here, but penalise the use of units e.g. grams) 1 [11]

Q33. (a) X (O–H) (alcohols) penalise acid or missing “alcohol” 1

Y C=O allow carbonyl 1

NOT acid 4

(b)

Allow conseq dibromocompounds following incorrect unbranched alkenes NOT allow dibromocompound consequent on a duplicate alkene NOT allow monobromocompounds if HBr added 3

6:3:1 either next to correct structure or to none 1

Page 63 of 64 Allow a mark for identifying correct dibromocompound with three peaks even if integration ratio is wrong 1

if 6:3:1 missing or wrong, no marks for splitting

Only award a mark for splitting if it is clear which integration number it refers to

6 singlet or drawn 1

3 doublet or drawn 1

1 quartet/quadruplet or drawn 1 (max 10 marks) [16]

Q34. B [1]

Q35. A [1]

Page 64 of 64

Name: ______Organic analysis and IR

Class: ______

Date: ______

Time: 293 minutes

Marks: 281 marks

Comments:

Page 1 of 82 Q1. The infrared spectrum of an organic compound is shown.

Which compound produces this spectrum?

A butanone

B ethanol

C pent-2-ene

D propanoic acid (Total 1 mark)

Q2. Which compound forms a molecular ion with a different precise molecular mass from the other three?

A butanone

B cyclobutanol

C dimethylpropane

D methylpropanal (Total 1 mark)

Q3. Test-tube reactions can be used to identify the functional groups in organic molecules.

Page 2 of 82 You are provided with samples of each of the four compounds.

Describe how you could distinguish between all four compounds using the minimum number of tests on each compound.

You should describe what would be observed in each test.

______

______(Total 6 marks)

Q4. Which compound gives this infrared spectrum?

A 1-bromobutane

Page 3 of 82 B butan-1-ol

C butanal

D butanoic acid (Total 1 mark)

Q5. A student was given unlabelled samples of pentan-1-ol, pent-1-ene, pentanoic acid and pentanal.

(a) Name the reagent(s) that the student could use to identify the sample that was pent- 1-ene. Describe the observation(s) that the student would make to confirm this.

Reagent(s) ______

______

Observation(s) ______(2)

(b) Name the reagent(s) that the student could use to identify the sample that was pentanoic acid.

Describe the observation(s) that the student would make to confirm this.

Reagent(s) ______

______

Observation(s) ______(2)

Describe the observation(s) that the student would make to confirm this.

Reagent(s) ______

______

Observation(s) ______

______

______(2)

(d) The student deduced that the spectrum in the image below was that of pentanal.

Page 4 of 82

Justify this deduction and suggest why this spectrum cannot be that of pentan-1-ol, pentanoic acid or pent-1-ene.

______

______(4) (Total 10 marks)

Q6. Chemists design synthetic routes to convert one organic compound into another.

Buta-1,3-diene, C, is converted into compound F as shown in the diagram below.

(a) State the IUPAC name of compound F.

Page 5 of 82 ______(1)

(b) Deduce the structure of compound D.

For each of the conversions in steps 1 and 2, suggest a reagent for the conversion and name the mechanism.

Suggest the type of reaction occurring in step 3.

Structure of D

Step 1 ______

______

Step 2 ______

______

Type of reaction in Step 3 ______

______(6)

State a reagent (or combination of reagents) that can be used in a test-tube reaction to distinguish between F and G.

Describe what you would observe when the reagent is added to each compound and the test tube is shaken.

Reagent(s) ______

______

Observation with F ______

Page 6 of 82 ______

______

Observation with G ______

______

______(3)

(d) Compounds F and G react to form a polymer.

Draw the repeating unit of the polymer.

(2)

(e) In an experiment, 0.930 kg of purified F were obtained from 1.11 dm3 of G (density 1.04 g cm−3).

Calculate the percentage yield.

Give your answer to the appropriate number of significant figures.

Percentage yield ______% (4)

(f) One reason for a yield of less than 100% in part (e) is that G reacts to form a number of other compounds.

The other compounds are all liquids at room temperature.

Name the technique that should be used to separate and collect each of these other compounds from the reaction mixture.

Include in your answer a description of the apparatus.

Your description of the apparatus can be either a description in words or a labelled sketch.

Name of technique ______

Apparatus

Page 7 of 82 (4) (Total 20 marks)

Q7. The infrared spectrum (Figure 1) and the 1H NMR spectrum (Figure 2) of compound R with molecular formula C6H14O are shown.

Figure 1

Figure 2

Page 8 of 82

The relative integration values for the NMR peaks are shown on Figure 2.

Deduce the structure of compound R by analysing Figure 1 and Figure 2. Explain each stage in your deductions.

Use Table A and Table B on the Data Sheet.

______

______(Total 8 marks)

Page 9 of 82 Q8. The compounds in the table all have a relative molecular mass of 58.0

(a) Explain why determining the precise relative molecular mass of propanal and prop-2-en-1-ol by mass spectrometry could not be used to distinguish between samples of these two compounds.

______

______(2)

(b) The infrared spectrum of one of these three compounds is shown below.

Use the spectrum to identify the compound. State the bond that you used to identify the compound and give its wavenumber range. You should only consider absorptions with wavenumbers greater than 1500 cm−1.

Compound ______

Bond used to identify compound ______

Wavenumber range of bond used to identify compound ______cm−1 (2)

Page 10 of 82 Justify this order in terms of intermolecular forces. (6) (Total 10 marks)

Q9. Compound R contains 61.0% carbon and 11.9% hydrogen by mass. The remainder is oxygen. The mass spectrum of R contains a molecular ion peak at m/z = 118.

(a) Use these data to show that the molecular formula of R is C6H14O2.

______

______(3)

(b) The infrared spectrum of R (C6H14O2) is shown below.

The proton n.m.r. spectrum of R contains five peaks. The chemical shift values, integration ratios and splitting patterns of these peaks are given in the table.

Chemical 3.8 3.2 3.1 1.4 1.1 shift/ppm

Integration ratio 2 3 1 2 6

Splitting patterns triplet singlet singlet triplet singlet

When R is warmed with acidified potassium dichromate(VI) a green solution is formed.

Page 11 of 82 Use Table A and Table B on the data sheet and all of the data provided in the question to deduce the structure of R.

In your answer, explain how you have used the data provided in the question. (9) (Total 12 marks)

Q10. The following pairs of compounds can be distinguished by simple test−tube reactions.

For each pair of compounds, give a reagent (or combination of reagents) that, when added separately to each compound, could be used to distinguish between them. State what is observed in each case.

(a) Butan−2−ol and 2−methylpropan−2−ol

Reagent ______

Observation with butan−2−ol

______

Observation with 2−methylpropan−2−ol

______

______(3)

(b) Propane and propene

Reagent ______

Observation with propane

______

Observation with propene

______

______(3)

Reagent ______

Observation with aqueous silver nitrate

______

Page 12 of 82 ______

Observation with aqueous sodium nitrate

______

______(3)

(d) Aqueous magnesium chloride and aqueous barium chloride

Reagent ______

Observation with aqueous magnesium chloride

______

Observation with aqueous barium chloride

______

______(3) (Total 12 marks)

Q11. Butane and propanal are compounds with Mr = 58.0, calculated using data from your Periodic Table.

(a) A mass spectrometer can be used to distinguish between samples of butane and propanal.

The table shows some precise relative atomic mass values.

Atom Precise relative atomic mass

1H 1.00794

12C 12.00000

(i) Use data from the table to show that, to 3 significant figures, a more accurate value for the Mr of butane is 58.1

______

______(1)

(ii) State why the precise relative atomic mass quoted in the table for the 12C

Page 13 of 82 isotope is exactly 12.00000

______

______(1)

(b) Draw a displayed formula for the organic product that is formed when propanal is oxidised by warm Tollens’ reagent. (1)

(c) Prop−2−en−1−ol is an isomer of propanal and can be polymerised to form a polymer represented by the following structure.

(i) Draw the structure of prop−2−en−1−ol. (1)

(ii) Deduce the type of polymerisation that results in the formation of this polymer from prop−2−en−1−ol.

______(1)

(iii) There are two functional groups in prop−2−en−1−ol. Each of these functional groups contains a bond with a characteristic absorption range in the infrared spectrum.

Use Table A on the Data Sheet to suggest a bond and its absorption range for each of the two functional groups.

Bond 1 ______Absorption range ______

Bond 2 ______Absorption range ______(2)

(d) Compound X is another isomer of propanal. The infrared spectrum of X shows an absorption in the range 1680−1750 cm−1.

(i) Draw the structure of X.

Page 14 of 82

(ii) Which of the following, A, B, C or D, represents the type of isomerism shown by X and propanal?

Write the correct letter, A, B, C or D, in the box.

A chain isomerism B E−Z isomerism C functional group isomerism D position isomerism

(1) (Total 9 marks)

Q12. The following five isomers, P, Q, R, S and T, were investigated using test-tube reactions and also using n.m.r. spectroscopy.

(a) A simple test-tube reaction can be used to distinguish between isomers P and S.

Identify a reagent (or combination of reagents) you could use. State what you would observe when both isomers are tested separately with this reagent or combination of reagents.

______

Page 15 of 82 (3)

(b) A simple test-tube reaction can be used to distinguish between isomer Q and all the other isomers.

Identify a reagent (or combination of reagents) you could use. State what you would observe when Q is tested with this reagent or combination of reagents.

______

______(2)

(c) State which one of the isomers, P, Q, R, S and T, has the least number of peaks in its 1H n.m.r. spectrum. Give the number of peaks for this isomer.

______

______(2)

(d) Write the molecular formula of the standard used in 13C n.m.r. spectroscopy. Give two reasons why this compound is used.

______

______(3)

(e) Figure 1 and Figure 2 show the 13C n.m.r. spectra of two of the five isomers.

Figure 1 Figure 2

Page 16 of 82

The structures of the five isomers are repeated to help you answer this question.

State which isomer produces the spectrum in Figure 1 and which isomer produces the spectrum in Figure 2.

Explain your answer.

You do not need to identify every peak in each spectrum. Use Table C on the Data Sheet to answer the question.

______

Page 17 of 82 ______

______

______(5)

(f) U and V are other isomers of P, Q, R, S and T. The 1H n.m.r. spectrum of U consists of two singlets. V is a cyclic alcohol that exists as optical isomers.

Draw the structure of U and the structure of V.

U V (2) (Total 17 marks)

Q13. The carboxylic acid 3-methylbutanoic acid is used to make esters for perfumes. The following scheme shows some of the reactions in the manufacture of this carboxylic acid.

(a) One of the steps in the mechanism for Reaction 1 involves the replacement of the functional group by bromine.

(i) Use your knowledge of organic reaction mechanisms to complete the mechanism for this step by drawing two curly arrows on the following equation.

(2)

(ii) Deduce the name of the mechanism in part (i).

Give the IUPAC name of (CH3)2CHCH2Br

______

Page 18 of 82 ______

______(2)

Deduce the name of the type of reaction that occurs in Reaction 3.

______

______(3)

(c) When 3-methylbutanoic acid reacts with ethanol in the presence of an acid catalyst, an equilibrium is established. The organic product is a pleasant-smelling ester.

(CH3)2CHCH2COOH + CH3CH2OH (CH3)2CHCH2COOCH2CH3 + H2O an ester

The carboxylic acid is very expensive and ethanol is inexpensive. In the manufacture of this ester, the mole ratio of carboxylic acid to ethanol used is 1 to 10 rather than 1 to 1.

(i) Use Le Chatelier’s principle to explain why a 1 to 10 mole ratio is used. In your explanation, you should not refer to cost.

______

Page 19 of 82 ______

(Extra space) ______

______(3)

(ii) Explain how a catalyst increases the rate of a reaction.

______

(Extra space) ______

______(2) (Total 12 marks)

Q14. (a) Ester 1 and Ester 2 were studied by 1H n.m.r. spectroscopy.

Ester 1 Ester 2

One of the two esters produced this spectrum.

ppm

Deduce which of the two esters produced the spectrum shown. In your answer, explain the position and splitting of the quartet peak at δ = 4.1 ppm in the spectrum.

Predict the δ value of the quartet peak in the spectrum of the other ester.

Use Table B on the Data Sheet.

Page 20 of 82 ______

______

______(4)

(b) Cetrimide is used as an antiseptic.

+ – [CH3(CH2)15N(CH3)3] Br

cetrimide

Name this type of compound.

Give the reagent that must be added to CH3(CH2)15NH2 to make cetrimide and state the reaction conditions.

Name the type of mechanism involved in this reaction.

______

______(4)

(c) Give a reagent that could be used in a test-tube reaction to distinguish between benzene and cyclohexene. Describe what you would see when the reagent is added to each compound and the test tube is shaken.

______

Page 21 of 82 ______

______

______(3) (Total 11 marks)

Q15. Ethanoic acid, propyl ethanoate and propan-1-ol are all colourless liquids. Esters do not give a positive result with any of the usual tests for functional groups.

State how you could use chemical tests to show the presence of ethanoic acid and propan-1-ol in a mixture of the acid, the alcohol and the ester.

______

______(Total 4 marks)

Q16. Explain how infrared spectroscopy can be used to show that an aldehyde is definitely pentanal.

______

______(Total 2 marks)

Q17. (a) A chemist discovered four unlabelled bottles of liquid, each of which contained a different pure organic compound. The compounds were known to be propan-1-ol, propanal, propanoic acid and 1-chloropropane.

Describe four different test-tube reactions, one for each compound, that could be used to identify the four organic compounds.

Page 22 of 82 Your answer should include the name of the organic compound, the reagent(s) used and the expected observation for each test.

______

(Extra space) ______

______

______(8)

(b) A fifth bottle was discovered labelled propan-2-ol. The chemist showed, using infrared spectroscopy, that the propan-2-ol was contaminated with propanone.

The chemist separated the two compounds using column chromatography. The column contained silica gel, a polar stationary phase.

The contaminated propan-2-ol was dissolved in hexane and poured into the column. Pure hexane was added slowly to the top of the column. Samples of the eluent (the solution leaving the bottom of the column) were collected.

• Suggest the chemical process that would cause a sample of propan-2-ol to become contaminated with propanone.

• State how the infrared spectrum showed the presence of propanone.

• Suggest why propanone was present in samples of the eluent collected first (those with shorter retention times), whereas samples containing propan-2-ol were collected later.

______

Page 23 of 82 ______

______

(Extra space) ______

______

______(4) (Total 12 marks)

Q18. Consider the five cyclic compounds, A, B, C, D and E.

Page 24 of 82 (a) The infrared spectra of compounds A, B, C and D are shown below.

Write the correct letter, A, B, C or D, in the box next to each spectrum. You may find it helpful to refer to Table 1 on the Data Sheet.

(i)

(1)

(ii)

(1)

(iii)

(1)

Page 25 of 82 (iv)

(1)

(b) A simple chemical test can be used to distinguish between cyclohexane (A) and cyclohexene (D). Give a reagent for this test and state what you would observe with each compound.

______

(Extra space) ______

______

______(3)

Give a reagent or combination of reagents that can be used for this reaction and state the type of reaction.

State the class of alcohols to which cyclohexanol belongs.

______

Page 26 of 82 ______

(Extra space) ______

______

______(3)

(d) Cyclohexane (A) can be converted into bromocyclohexane (E) by a reaction that is similar to the reaction of methane either with chlorine or with bromine.

Name and outline a mechanism for the reaction of methane (CH4) with bromine to form bromomethane (CH3Br). Give one condition for this reaction to occur. Write an equation for each step in your mechanism.

______

(Extra space) ______

______

______(5) (Total 15 marks)

Q19. Mass spectrometry is used by organic chemists to help distinguish between different compounds.

Four isomers of C9H10O, shown below, were analysed by mass spectrometry.

Page 27 of 82

The mass spectra obtained from these four isomers were labelled in random order as I, II, III and IV.

Each spectrum contained a molecular ion peak at m/z = 134

The data in the table below show the m/z values greater than 100 for the major peaks in each spectrum due to fragmentation of the molecular ion. The table also shows where no major peaks occurred.

Spectrum m/z values for major peaks No major peak at m/z

I 119 133, 105

II 133, 119 and 105

III 133, 105 119

IV 105 133, 119

(a) Two of the molecular ions fragmented to form an ion with m/z = 133 by losing a radical. Identify the radical that was lost.

______(1)

(b) Two of the molecular ions fragmented to form an ion with m/z = 119 by losing a radical. Identify the radical that was lost.

______(1)

Identify two different radicals with Mr = 29 that could have been lost.

Radical 1 ______

Radical 2 ______(2)

Page 28 of 82 (d) Consider the structures of the four isomers and the fragmentations indicated in parts (a) to (c). Write the letter A, B, C or D, in the appropriate box below, to identify the compound that produces each spectrum.

Spectrum I

Spectrum II

Spectrum III

Spectrum IV

(4) (Total 8 marks)

Q20. Compound X (C6H12O2) was analysed by infrared spectroscopy and by proton nuclear magnetic resonance spectroscopy.

(a) The infrared spectrum of X is shown below. Use Table 1 on the Data Sheet to help you answer the question.

Identify the functional group that causes the absorption at 3450cm–1 in the spectrum.

______(1)

(b) The proton n.m.r. spectrum of X consists of 4 singlet peaks.

Page 29 of 82 The table below gives the chemical shift for each of these peaks, together with their integration values.

δ /ppm 1.2 2.2 2.6 3.8

Integration value 6 3 2 1

Use Table 2 on the Data Sheet to help you answer the following questions.

Use the chemical shift and the integration data to show what can be deduced about the structure of X from the presence of the following in its proton n.m.r. spectrum.

(i) The peak at δ = 2.6

______(1)

(ii) The peak at δ = 2.2

______(1)

(iii) The peak at δ = 1.2

______(1)

(iv) Deduce the structure of X (C6H12O2)

(1) (Total 5 marks)

Q21. A sample of an alcohol was thought to be contaminated with an alkene. Give a reagent that could be used to confirm the presence of an alkene. State what you would observe.

Reagent ______

Page 30 of 82 Observation ______(Total 2 marks)

Q22. (a) Propanoic acid can be made from propan-1-ol by oxidation using acidified potassium dichromate(VI). Propanal is formed as an intermediate during this oxidation.

(i) State the colour of the chromium species after the potassium dichromate(VI) has reacted.

______(1)

(ii) Describe the experimental conditions and the practical method used to ensure that the acid is obtained in a high yield. Draw a diagram of the assembled apparatus you would use.

Conditions ______

______

Apparatus (4)

(iii) Describe the different experimental conditions necessary to produce propanal in high yield rather than propanoic acid.

______

______(2)

(b) Propan-1-ol is a volatile, flammable liquid. Give one safety precaution that should be used during the reaction to minimise this hazard.

______(1)

(c) A student followed the progress of the oxidation of propan-1-ol to propanoic acid by extracting the organic compounds from one sample of reaction mixture.

(i) Give a chemical reagent which would enable the student to confirm the presence of propanal in the extracted compounds. State what you would observe when propanal reacts with this reagent.

Reagent ______

Observation ______

______(2)

(ii) Give a chemical reagent that would enable the student to confirm the presence of propanoic acid in the extracted compounds.

Page 31 of 82 State what you would observe when propanoic acid reacts with this reagent.

Reagent ______

Observation ______

______(2)

(d) Predict which one of the compounds, propan-1-ol, propanal and propanoic acid will have the highest boiling point. Explain your answer.

Prediction ______

Explanation ______

______

______(3) (Total 15 marks)

Q23. Samples of 1-chloropropane and ethanoyl chloride can be distinguished by the addition of an aqueous solution of silver nitrate. State what you would observe with each sample.

Observation with 1-chloropropane

______

Observation with ethanoyl chloride.

______

______(Total 2 marks)

Q24. A student used the infrared spectra of water vapour and of carbon dioxide to try to find a link between infrared radiation and global warming.

Page 32 of 82

(i) Use information from the infrared spectra to deduce one reason why the student concluded that water vapour is a more effective greenhouse gas than carbon dioxide.

______

______(1)

(ii) Use your knowledge of the bonds in CO2 to state why the infrared spectrum of carbon dioxide is not as might be predicted from the data provided in Table 1 on the Data Sheet.

______

______(2) (Total 3 marks)

Q25.

Page 33 of 82 The alkene (Z)-3-methylpent-2-ene reacts with hydrogen bromide as shown below.

(a) (i) Name the major product P.

______(1)

(ii) Name the mechanism for these reactions.

______(1)

(iii) Draw the displayed formula for the minor product Q and state the type of structural isomerism shown by P and Q.

Displayed formula for Q

Type of structural isomerism ______(2)

(iv) Draw the structure of the (E)-stereoisomer of 3-methylpent-2-ene.

(1)

(b) The infrared spectra of two compounds R and S are shown below. R and S have the molecular formula C6H12 and are structural isomers of 3-methylpent-2-ene. R is an unsaturated hydrocarbon and S is a saturated hydrocarbon.

Spectrum 1

Page 34 of 82

Spectrum 2

(i) Identify the infrared Spectrum 1 or 2 that represents compound R. Use information from the infrared spectra to give one reason for your answer. You may find it helpful to refer to Table 1 on the Data Sheet.

R is represented by Spectrum ______

Reason ______

______(2)

(ii) State the type of structural isomerism shown by R and S.

______(1)

(iii) Name one possible compound which could be S.

______(1) (Total 9 marks)

Q26. Infrared spectroscopy can be used to distinguish between esters, alcohols and carboxylic

Page 35 of 82 acids.

Use the table below, where appropriate, to answer the following questions.

Infrared absorption data

Bond Wavenumber / cm−1

N – H 3300 – 3500 (amines)

O – H 3230 – 3550 (alcohols)

C – H 2850 – 3300

O – H 2500 – 3000 (acids)

C ≡ N 2220 – 2260

C = O 1680 – 1750

C = C 1620 – 1680

C – O 1000 – 1300

C – C 750 – 1100

(a) Identify an absorption that would enable you to distinguish between methyl ethanoate and ethanoic acid.

______(1)

(b) Identify an absorption that would enable you to distinguish between methanol and ethanoic acid.

______(1)

______

______(2) (Total 4 marks)

Page 36 of 82 Q27. Pure hydrogen peroxide is a colourless liquid with a boiling point of 150 °C. Hydrogen peroxide was originally produced commercially in a two-stage process. In the first stage barium was heated in air to form barium peroxide. In the second stage barium peroxide was added to aqueous nitric acid. The equations for the reactions are shown below.

Stage 1 Ba(s) + O2(g) BaO2(s)

Stage 2 BaO2(s) + 2HNO3(aq) H2O2(aq) + Ba(NO 3)2(aq)12

(a) Suggest one method of separating hydrogen peroxide from the reaction mixture in Stage 2.

______

______(1)

(b) Apart from cost, suggest one reason why nitric acid was eventually replaced by sulfuric acid in Stage 2.

______

______(1)

(c) Suggest one reason why infrared spectroscopy could not be used to indicate the presence of a small amount of water in hydrogen peroxide.

______

______(1) (Total 3 marks)

Q28. Butan-2-ol can be oxidised by acidified potassium dichromate(VI) to form butanone as shown by the following equation.

CH3CH2CH(OH)CH3 + [O] → CH3CH2COCH3 + H2O

(a) State the class of alcohol to which butan-2-ol belongs.

______(1)

(b) The infrared spectrum shown below is either that of butan-2-ol or that of butanone.

Page 37 of 82

Identify the compound to which this infrared spectrum refers.

Explain your answer.

You may find it helpful to refer to the table of infrared absorption data on the back of the Periodic Table (Table 1).

Identity of the compound ______

Explanation ______

______

______(3)

(c) Draw the displayed formula of the alcohol C4H9OH which is resistant to oxidation by acidified potassium dichromate(VI).

______(1) (Total 5 marks)

Q29. (a) Alcohols can be classed as primary, secondary or tertiary. Draw possible structures for a primary, a secondary and a tertiary alcohol which have the molecular formula C4H8O. Which of the structures you have drawn cannot be oxidised by potassium

Page 38 of 82 dichromate in acid solution? (4)

(b) Explain what is meant by the fingerprint region of an infra-red spectrum. State how it is used to confirm the identity of organic molecules such as the primary, secondary and tertiary alcohols of molecular formula C4H8O. (2)

(c) Each of the parts below concerns a different pair of isomers. Deduce one possible structural formula for each of the species A to F. Use, where appropriate, the table of infra-red absorption data given on the data sheet.

(i) A and B have the molecular formula C3H8O. A has a broad absorption band at 3300 cm–1 in its infra-red spectrum, but B does not.

(ii) C and D have the molecular formula C5H10. C has a weak absorption band at 1650 cm–1 in its infra-red spectrum, but D does not.

(iii) E and F have the molecular formula C3H6O and both have strong absorption bands at about 1700 cm–1 in their infra-red spectra. E reacts with Tollens’ reagent but F does not. (6) (Total 12 marks)

Q30. It is necessary to use several analytical techniques to determine the structure of an unknown compound.

An analytical chemist was asked to determine the structure of compound Q which was found in a waste tank in a mixture of volatile liquids.

Compound Q has the molecular formula C4H7ClO. It is a volatile liquid which does not produce misty fumes when added to water.

(a) Suggest how the chemist could obtain a sample of Q for analysis from the mixture of volatile liquids.

______(1)

(b) The infra-red spectrum of Q contains a major absorption at 1724 cm–1. Identify the bond which causes this absorption.

______(1)

(c) The mass spectrum of Q contains two molecular ion peaks at m/z = 106 and m/z = 108. It also has a major peak at m/z = 43.

(i) Suggest why there are two molecular ion peaks.

______

(ii) A fragment ion produced from Q has m/z = 43 and contains atoms of three different elements. Identify this fragment ion and write an equation showing its

Page 39 of 82 formation from the molecular ion of Q.

Fragment ion ______

Equation ______(3)

(d) The proton n.m.r. spectrum of Q was recorded.

(i) Suggest a suitable solvent for use in recording this spectrum of Q.

______

(ii) Give the formula of the standard reference compound used in recording proton n.m.r. spectra.

______(2)

(e) The proton n.m.r. spectrum of Q shows 3 peaks. Complete the table below to show the number of adjacent, non-equivalent protons responsible for the splitting patterns.

Peak 1 Peak 2 Peak 3

Integration value 3 3 1

Splitting pattern doublet singlet quartet

Number of adjacent, 1 non-equivalent protons

(1)

(f) Using the information in parts (a), (b) and (d) deduce the structure of compound Q.

(1)

(g) A structural isomer of Q reacts with cold water to produce misty fumes. Suggest a structure for this isomer.

(1) (Total 10 marks)

Page 40 of 82 Q31. (a) The infra-red spectrum of compound A, C3H6O2, is shown below.

Identify the functional groups which cause the absorptions labelled X and Y.

Using this information draw the structures of the three possible structural isomers for A.

Label as A the structure which represents a pair of optical isomers. (6)

(b) Draw the structures of the three branched-chain alkenes with molecular formula C5H10

Draw the structures of the three dibromoalkanes, C5H10Br2, formed when these three alkenes react with bromine.

One of these dibromoalkanes has only three peaks in its proton n.m.r. spectrum. Deduce the integration ratio and the splitting patterns of these three peaks. (10) (Total 16 marks)

Q32. This question concerns four isomers, W, X, Y and Z, with the molecular formula C5H10O2

(a) The proton n.m.r. spectrum of W shows 4 peaks. The table below gives the chemical shifts, δ values, for each of these peaks, together with their splitting patterns and integration values.

δ/ppm 2.18 2.59 3.33 3.64

Splitting pattern singlet triplet singlet triplet

Integration value 3 2 3 2

State what can be deduced about the structure of W from the presence of the

Page 41 of 82 following in its n.m.r. spectrum.

(i) The singlet peak at δ = 2.18

______

(ii) The singlet peak at δ = 3.33

______

(iii) Two triplet peaks.

______

(iv) Hence, deduce the structure of W.

(4)

(b) The infra-red spectrum of X is shown below.

(i) What can be deduced from the broad absorption centred on 3000 cm–1 in the infra-red spectrum of X?

______

(ii) Given that the proton n.m.r. spectrum of X contains only two peaks with the

Page 42 of 82 integration ratio 9:1, deduce the structure of X.

(2)

Identify the two reagents you could use in a simple chemical test to distinguish between Y and Z. State what you would observe when each of Y and Z is tested with a mixture of these two reagents.

Reagents ______

Observation with Y ______

Observation with Z ______(3) (Total 9 marks)

Q33. This question is about the reaction between propanone and an excess of ethane-1,2-diol, the equation for which is given below.

In a typical procedure, a mixture of 1.00 g of propanone, 5.00 g of ethane-1,2-diol and 0.100 g of benzenesulphonic acid, C6H5SO3H, is heated under reflux in an inert solvent. Benzenesulphonic acid is a strong acid.

The products would not have an absorption in the infra-red at

A 1050 cm−1

B 1720 cm−1

C 2950 cm−1

D 3400 cm−1

Page 43 of 82 (Total 1 mark)

Q34. Spectral data for use in this question are provided below the Periodic Table (first item on the database).

Compound Q has the molecular formula C4H8O2

(a) The infra-red spectrum of Q is shown below.

Identify the type of bond causing the absorption labelled R and that causing the absorption labelled S.

R ______

S ______(2)

(b) Q does not react with Tollens’ reagent or Fehling’s solution. Identify a functional group which would react with these reagents and therefore cannot be present in Q.

______(1)

(i) Give two reasons why TMS is a suitable standard.

Reason 1 ______

Reason 2 ______

(ii) Give an example of a solvent which is suitable for use in recording an n.m.r. spectrum. Give a reason for your choice.

Solvent ______

Page 44 of 82 Reason ______(4)

(d) The proton n.m.r. spectrum of Q shows 4 peaks.

The table below gives δ values for each of these peaks together with their splitting patterns and integration values.

δ/ppm 2.20 2.69 3.40 3.84

Splitting pattern singlet triplet singlet triplet

Integration value 3 2 1 2

What can be deduced about the structure of Q from the presence of the following in its n.m.r. spectrum?

(i) The singlet peak at δ = 2.20

______

(ii) The singlet peak at δ = 3.40

______

(iii) Two triplet peaks

______(3)

(e) Using your answers to parts (a), (b) and (d), deduce the structure of compound Q.

(1) (Total 11 marks)

Q35. Certain chemical tests were performed on the pain-relief drug ibuprofen. The results of these tests are given in the table below.

Test Result

Aqueous sodium carbonate Effervescence

Bromine water Remained orange

Acidified potassium dichromate(VI) and heat Remained orange

Page 45 of 82 Fehling’s solution and heat Remained blue

Which one of the following functional groups do these results suggest that ibuprofen contains?

D (Total 1 mark)

Page 46 of 82 Mark schemes

Q1. A [1]

Q2. C [1]

Q3. This question is marked using Levels of Response. Refer to the Mark Scheme Instructions for Examiners for guidance.

Level 3 (5 – 6 marks) All stages are covered and each stage is generally correct and virtually complete. Answer is communicated coherently and shows a logical progression from Stage 1 to Stages 2 and 3 to distinguish all the compounds with results for all remaining compounds stated. Describing subsequent organic test on product (unnecessary) - limits to lower mark in level

Level 2 (3 – 4 marks) All stages are covered but stage(s) may be incomplete or may contain inaccuracies OR two stages are covered and are generally correct and virtually complete. Answer is communicated mainly coherently and shows a logical progression from Stage 1 to Stages 2 and 3. Describing subsequent organic test on product (unnecessary) - limits to lower mark in level

Level 1 (1 – 2 marks) Two stages are covered but stage(s) may be incomplete or may contain inaccuracies OR only one stage is covered but is generally correct and virtually complete. Answer includes isolated statements but these are not presented in a logical order.

Level 0 (0 marks) Insufficient correct chemistry to gain a mark.

Indicative chemistry content

Stage 1: An initial test to separate into two groups (2 groups of 2 OR 1 group of 3 and 1 group of 1)

Stage 2: A second test to distinguish within a group or to separate into two further groups

Stage 3: A third test leads to a set of results/observations which distinguishes between all 4 compounds

Tests must include reagent and observation which identifies compound(s)

−COOH a) NaHCO3 / Na2CO3 (or correct alternative)

Page 47 of 82 b) effervescence /gas turns limewater milky c) K and /or M but not L and/or N -OH and -CHO d) acidified K2Cr2O7 e) solution turns green f) K and/or L and/or N but not M -CHO g) Fehlings OR Tollens h) red ppt OR silver mirror i) N only but not K and/or L and/or M -Br j) Silver nitrate k) cream ppt l) L and/or N but not K and/or M

Isolated tests on individual compounds - max LEVEL 2 Isolated tests not linked to any compound – max LEVEL 1 Penalise observation if deduction wrong, but allow observation if deduction incomplete

Alternative tests

-COOH -COOH -OH only a) named alcohol & a) named indicator m) named carboxylic H2SO4 b) correct colour acid & H2SO4 b) sweet smell (of c) K and /or M but not n) sweet smell (of ester) L and/or N ester) c) K and /or M but not o) K and/or L but not L and/or N M and /or N

Test Tests K L M N for

a) NaHCO3 / Mg / K M ✓ ✘ ✓ ✘ Indicator

+ d) K2Cr2O7 / H K L N ✓ ✓ ✘ ✓

g) Fehlings / N ✘ ✘ ✘ ✓ Tollens

j) AgNO3 see L N ✘ ✓ ✘ ✓ Note *

a) named alcohol & K M ✓ ✘ ✓ ✘ H2SO4

m) named K L ✓ ✓ ✘ ✘ carboxylic

Page 48 of 82 acid & H2SO4

Note * allow NaOH then HNO3, AgNO3 as one test; but treat NaOH, AgNO3 without acid as incomplete,so can mark on. [6]

Q4. C [1]

Q5. (a) Bromine (water) 1

Colour change from orange to colourless 1

(b) Add sodium hydrogencarbonate (or alternative named carbonate) Allow suitable correct alternative test e.g. Test the pH with named indicator (e.g. Universal Indicator) 1

Propanoic acid will produce effervescence / bubbles Propanoic acid would turn Universal Indicator red 1

(Colourless solution to) silver mirror 1

Fehling’s solution

(Blue solution to) brick red precipitate

(d) Absorption at 1680–1750 cm−1 caused by C=O 1

No absorption at 1620−1680 cm−1 caused by C=C 1

No absorption at 3230–3550 cm−1 due to −OH (alcohol) 1

No absorption at 2500–3000 cm−1 due to −OH (acid) 1 [10]

Q6. (a) 2,3-dimethylbutane(-1,4-)dioic acid Penalise other numbers.

Page 49 of 82 Ignore hyphens, commas, spaces. 1

(b)

Allow displayed formula

Step 1:

HBr 1

Electrophilic addition 1

Step 2:

KCN Not HCN, not KCN with acid. 1

Nucleophilic substitution 1

Step 3:

Hydrolysis 1

(c)

Mark Reagent 1

Observation with 1 F Observation with 1 G

K2Cr2O7 & H2SO4 (allow Mg Na2CO3 or NaHCO3 acidified)

F: no visible change F: effervescence F: effervescence

G: orange to green G: no visible change G: no visible change

Page 50 of 82 Named alcohol and conc. Named carboxylic acid and sulfuric acid conc. sulfuric acid

F: pleasant smell F: no visible change

G: no visible change G: pleasant smell

(d)

Two ester groups. 1 One unit only. Must have trailing bonds. Ignore n and brackets. 1

(e) Mass of G = (1.11 × 103) cm3 × 1.04 g cm−3 = 1154 g 65.1 scores 4 marks. 1

Amount of G = 9.78 mols 1

Amount of F (actual) = =

6.37 mol

Expected mass of F = 9.78 × (Mr =)

146 = 1428 g 1

% yield = × 100 = 65.1(%)

Page 51 of 82 M4 answer must be to 3 significant figures. 1

(f) Fractional distillation

A rough labelled sketch illustrating these points scores the marks. 1 Apparatus for fractional distillation must clearly work with fractionating column. 1 Fractionating column and thermometer. 1 Condenser / water jacket. Ignore heat source. 1 [20]

Q7. IR Extended response

Absorption at 3360 cm–1 shows OH alcohol present Deduction of correct structure without explanation scores maximum of 4 marks as this does not show a clear, coherent line of reasoning. M1 1

NMR

There are 4 peaks which indicates 4 different environments of hydrogen Maximum of 6 marks if no structure given OR if coherent logic not displayed in the explanations of how two of OH, CH3 and CH2CH3 are identified. M2 1

Page 52 of 82 The integration ratio = 1.6 : 0.4 : 1.2 : 2.4

The simplest whole number ratio is 4 : 1 : 3 : 6 M3 1

The singlet (integ 1) must be caused by H in OH alcohol M4 1

The singlet (integ 3) must be due to a CH3 group with no adjacent H M5 1

Quartet + triplet suggest CH2CH3 group M6 1

Integration 4 and integration 6 indicates two equivalent CH2CH3 groups M7 1

M8 1 [8]

Q8. (a) M1 have the same molecular formula or are C3H6O or both have the same number/amount of each type of atom or same amount of each element or are isomers Not just the same atoms; 1

M2 identical / exactly the same / same precise (relative) molecular mass / formula mass / Mr

Same (relative) molecular mass / formula mass / Mr is NOT enough got score M2 Allow same accurate (relative) molecular mass / formula mass / Mr Ignore reference to number of decimal places 1

(b) M1 prop-2-en-1-ol Must refer to this compound clearly by name or structure (not to alcohol alone); ignore minor slips in name/structure 1

M2 O(-)H (alcohol) and 3230–3550 (cm−1), or C=C and 1620–1680 (cm−1)

Page 53 of 82 Marked independently from M1 Could score from bond labelled on correct signal on spectrum Allow any value within these ranges If additional incorrect signals given penalise M2 Ignore signals below 1500 cm−1 and C-H signals 1

(c) (i) Determine the level by looking at the chemical content. (NB - If there is clear breakage of covalent bonds then max level 2 (max 3 marks).

(ii) The mark within that level is then determined by looking at how coherent and logical the answer is and by use of terminology; start at the higher mark and penalise poor terminology/explanation; examples of terminology that would reduce the mark to the lower one:

• reference to van der Waals ‘bonds’ or dipole-dipole ‘bonds in relevant compounds that are being credited • uncertainty about whether hydrogen bonds are the O-H bonds within or are forces/bonds between molecules (if the alcohol is being credited) • use of ‘vdw’ or ‘dip-dip’ unless these terms ‘van der Waals’ for ‘dipole-dipole’ have been used elsewhere in answer (note that IMF and H-bond would not be penalised)

(iii) If the answer does not achieve level 1, then 1 mark maximum could be scored for any correct point from the list of indicative content

Level 3 • Relative order of boiling points of all three compounds • Strongest intermolecular force of all three compounds identified • Answer explains this coherently and logically and uses correct terminology for all three compounds 5-6 marks

Level 2 • Relative boiling points of two compounds correctly compared • Strongest intermolecular force for these two compounds correctly identified • Answer explains this coherently and logically and uses correct terminology for these two compounds 3-4 marks

Level 1 • One compound with the highest or lowest boiling point is correctly identified • Strongest intermolecular force for that one compound identified • Answer explains this coherently and logically and uses correct terminology for this one compound • Allow 1 mark for individual correct point from indicative content on the right if no other mark scored 1-2 marks

Level 0 None of the indicative chemistry content given. 0 marks Indicative chemistry content: • Correct order (highest to lowest) = prop-2-en-1-ol > propanal > butane

Page 54 of 82 • Prop-2-en-1-ol has hydrogen bonds • Propanal has (permanent) dipole-dipole forces • Butane has van der Waals’ forces • Strength of intermolecular forces: hydrogen bonds > dipole-dipole > van der Waals (Note - actual values for reference are prop-2-en-1-ol 97°C, propanal 46°C and butane −1°C) [10]

Q9. (a) Method 1

M1 %O = 27.1

M2 3 7 1

M3 C3H7O = 59 which is half of Mr so MF = 2EF

Method 2

M1 61% of 118 = 72.0 and 11.9% of 118 = 14.0

M2 72 + 14 = 86 so oxygen = 32 out of 118

OR 27.1% of 118 = 32.0

M3 Method 3 Alternative using given molecular formula

(b) For this question, marks can be awarded either for a description of how the structure is derived or from the given structure itself. The maximum mark to be awarded is nine from the ten marks listed.

Page 55 of 82 Marks fall into three sections:

• Infrared evidence : two marks are available for use of the infrared evidence, (M1 and M10)

• Chemical evidence: one mark is available for use of the chemical evidence (M2)

• N.m.r. evidence: six marks are available for use of the n.m.r. evidence (M3 – M8 inclusive) plus one mark (M9) for a completely correct structure.

Suggested procedure for marking

First look at the infrared spectrum: marks M1 and M10 may be scored there or in the written answer.

Then look for use of the acidified potassium dichromate(VI) evidence, (M2).

Then look at the final structure: this may lead to the award of marks M3 to M9 as shown on the structures below.

Beware contradictions, e.g. using the chemical evidence they may state that R is a primary or secondary alcohol but then draw a tertiary alcohol. This will lose M2 but may score M3.

The written ‘evidence’ frequently simply contains extracts from the Table B on the Data Sheet and, if only this is given, is unlikely to score many marks.

Described Or drawn

M1 Infared peak/absorbance at 3400 (cm-1) = O-H alcohol (reference to ir spectrum needed) Note: please check the spectrum If peak at 3000 (cm-1) is identified as acid then cannot score M1 (contradiction)

M10 Either no peak between 1680-1750 (cm-1) so no C=O or not aldehyde/acid OR peak at 1000-1300 (cm-1) so C–O present Apply list principle to IR analysis for M10

M2 (Acidified potassium dichromate(VI) turns green) so primary alcohol or secondary alcohol or not tertiary alcohol Ignore aldehyde here Lose M2 if just tertiary alcohol in structure

M3 δ = 3.1 singlet or integration = 1 is O-H Award M3 if structure has 1 O-H group only (can be primary, secondary or tertiary) Lose M3 if more than one OH group shown

M4 two triplets at 1.4 & 3.8 = –CH2–CH2–

Allow –CH2–CH2–CH2–

Page 56 of 82 M5 δ = 3.8 means CH2 attached to O (in ether NOT ester)

Allow O–CH2–CH2–CH2–C

δ = 1.4 means CH2 attached to C (but not to C=O)

M6 δ = 1.1 (singlet) integration 6 = 2 × equivalent CH3 on same C

–C(CH3)2–

M7 δ = 1.1 singlet so no H attached to –C(CH3)2-

R–C(CH3)2–R

M8 δ = 3.2 singlet integration 3 = -OCH3

–OCH3

M9 For completely correct If no structure given then Max 8 R is

This close alternative

would not score M9, but could score up to 8 marks [12]

Q10. (a) M1 acidified potassium dichromate or K2Cr2O7 / H2SO4

+ OR K2Cr2O7 / H OR acidified K2Cr2O7

M2 (orange to) green solution OR goes green

Page 57 of 82 Alternative using KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate or KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 colourless solution OR goes colourless

M3 (solution) remains purple or no reaction or no (observed) change For M1 If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark on

Credit alkaline KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green 3

(b) M1 (Shake with) Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)

M2 (stays) orange / red / yellow / brown / the same

OR no reaction OR no (observed) change

OR as alternatives

Use KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate OR KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 (stays) purple or no reaction or no (observed) change

M3 decolourised / goes colourless / loses its colour

Use iodine

M1 iodine or I2 / KI or iodine solution

M2 no change

M3 decolourised / goes colourless / loses its colour

Page 58 of 82 Use concentrated sulfuric acid

M1 concentrated H2SO4

M2 no change

M3 brown For M1, it must be a whole reagent and / or correct formula For M1 penalise incorrect attempt at correct formula, but mark M2 and M3 With potassium manganate(VII) If incomplete / inaccurate attempt at reagent e.g. “manganate” or “manganate(IV)” or incorrect formula or no acid, penalise M1 only and mark on

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble iodide including HI

M2 yellow precipitate or yellow solid / yellow suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble bromide including HBr

M2 cream precipitate or cream solid / cream suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 NaOH or KOH or any soluble carbonate

M2 brown precipitate or brown solid / brown suspension with NaOH / KOH (white precipitate / solid / suspension with carbonate)

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear If no reagent or incorrect reagent or insoluble chloride in M1,

Page 59 of 82 CE = 0 and no marks for M1, M2 or M3 Allow chlorine water If incomplete reagent (e.g. chloride ions) or inaccurate attempt at formula of chosen chloride, or chlorine, penalise M1 only and mark on For M2 require the word “white” and some reference to a solid. Ignore “cloudy solution” OR “suspension” (similarly for the alternatives) For M3 Ignore “nothing (happens)” Ignore “no observation” Ignore “clear” on its own Ignore “dissolves” 3

(d) M1 Any soluble sulfate including (dilute or aqueous) sulfuric acid

M2 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

M3 white precipitate or white solid / white suspension If no reagent or incorrect reagent or insoluble sulfate in M1, CE = 0 and no marks for M1, M2 or M3

OR as an alternative

M1 NaOH or KOH

M2 white precipitate or white solid / white suspension

If M1 uses NH3 (dilute or concentrated) penalise M1 only and mark on 3 [12]

Page 60 of 82 Q11. (a) (i) C4H10

Mr = 4(12.00000) + 10(1.00794)

= 58.07940 or 58.0794 or 58.079 or 58.08

and 58.1 Working is essential, leading to the final value of 58.1 which must be stated in addition to one of the four numbers underlined 1

(ii) By definition OR The standard / reference (value / isotope) Reference to 12C alone is not enough 1

(b)

All bonds and atoms must be drawn Give credit for the displayed formula for the anion 1

(c) (i) H2C = CHCH2OH Any correct representation including correct use of “sticks”. Require the double bond to be shown 1

(ii) Addition (polymerisation) ONLY this answer 1

(iii) M1 C = C (in range) 1620 to 1680 (cm−1)

M2 O ‒ H (in range) 3230 to 3550 (cm−1) Award one mark for two correct ranges but a failure to draw out the C = C or O‒H bonds 2

(d) (i) CH3COCH3 Any correct representation including correct use of “sticks” 1

(ii) C 1 [9]

Q12.

Page 61 of 82 (a) Reagent

Acidified K2Cr2O7

Acidified KMnO4

I2 / NaOH

Named RCOOH with HCl or H2SO4

Named RCOCl Allow names including potassium permanganate Wrong or no reagent CE = 0 1

P (ketone) no reaction no reaction Yellow ppt no reaction no reaction Penalise incorrect formulae or incomplete reagent, such as K2Cr2O7 or acidified dichromate, but mark on. 1

S (2° alcohol) (orange to) green (purple to) colourless no reaction fruity or sweet smell Misty fumes Allow no change or nvc but penalise nothing or no observation If 2 reagents added sequentially or 2 different reagents used for P and S then CE = 0 1

(b) Tollens’ silver mirror / solid 1

Fehling’s / Benedicts red ppt 1

(d) C4H12Si

Page 62 of 82 Must be molecular formula Wrong substance CE = 0 for clip 1

Any two from • One or single peak OR all (four) carbon atoms are equivalent or one environment 1 • upfield from others or far away from others or far to right • non toxic OR inert • low boiling point or volatile or easy removed from sample Ignore and don’t credit single peak linked to 12 equivalent H or has a peak at δ = 0 but use list principle for wrong statements 1 1

(e) Figure 1 is R If not R cannot score M2

M1 1

90−150 (ppm) or value in range is (two peaks for) C = C / alkene

M2 1

Figure 2 is T If not T cannot score M4 or M5

M3 1

50-90 (ppm) or value in range is C—O or alcohol or ether

M4 1

two peaks (so not S which would have only one)

M5 1

(f)

Answers include

Page 63 of 82

Not allow S

because V must be an isomer of S [17]

Q13. (a) (i) M1 double-headed curly arrow from the lone pair of the bromide ion to the C atom of the CH2 Penalise additional arrows.

M2 double-headed arrow from the bond to the O atom

As follows

(ii) M1 nucleophilic substitution M1 both words needed (allow phonetic spelling).

M2 1-bromo(-2-)methylpropane M2 Require correct spelling in the name but ignore any hyphens or commas. 2

(b) M1 hydrolysis For M1 give credit for ‘hydration’ on this occasion only.

M2 C≡N with absorption range 2220–2260 (cm−1)

Page 64 of 82 Credit 1 mark from M2 and M3 for identifying C≡N and either O–H(acids) or C=O or C–O without reference to wavenumbers or with incorrect wavenumbers.

M3 O–H(acids) with absorption range 2500–3000 (cm−1)

C=O with absorption range 1680–1750 (cm−1)

C–O with absorption range 1000–1300 (cm−1) Apply the list principle to M3 3

M2 (By Le Chatelierߣs principle) the position of equilibrium is driven / shifts / moves to the right / L to R / in the forward direction / to the product(s)

M3 – requires a correct statement in M2

(The position of equilibrium moves)

to oppose the increased concentration of ethanol

to oppose the increased moles of ethanol

to lower the concentration of ethanol

to oppose the change and decrease the ethanol If no reference to M1, marks M2 and M3 can still score BUT if M1 is incorrect CE=0 If there is reference to ‘pressure’ award M1 ONLY. 3

(ii) M1

Catalysts provide an alternative route / pathway / mechanism

surface adsorption / surface reaction occurs For M1, not simply ‘provides a surface’ as the only statement. M1 may be scored by reference to a specific example.

that has a lower / reduced activation energy

lowers / reduces the activation energy Penalise M2 for reference to an increase in the energy of the

Page 65 of 82 molecules. For M2, the student may use a definition of activation energy without referring to the term. Reference to an increase in successful collisions in unit time alone is not sufficient for M2 since it does not explain why this has occurred. 2 [12]

Q14. (a) M1 Ester 1 If Ester 2, can score M3 only. 1

M2 peak at δ = 4.1 due to

When marking M2 and M3, check any annotation of structures in the stem at the top of the page. 1

M3 (δ = 4.1 peak is) quartet as adjacent / next to / attached to CH3 1

M4 Other spectrum quartet at δ = 2.1-2.6 (or value in this range) 1

(b) M1 Quaternary (alkyl) ammonium salt / bromide 1

M2 CH3Br or bromomethane Penalise contradictory formula and name. 1

M3 Excess ( CH3Br or bromomethane)

Mention of acid eg H2SO4 OR alkali eg NaOH loses both M2 and M3. 1

M4 Nucleophilic substitution Can only score M3 if reagent correct. Ignore alcohol or ethanol (conditions) or Temp. 1

(c)

Bromine Acidified KMnO4

(penalise Br (Penalise missing but acid mark on) but mark on)

Wrong reagent = no marks. If bromine colour stated it must be red, yellow, orange,

Page 66 of 82 brown or any combination, penalise wrong starting colour. 1

Benzene no reaction / colo no reaction / colour ur remains / no remains / no (visible) (visible) change change

Ignore ‘clear’, ‘nothing’. Allow colour fades slowly. Allow ‘nvc’ for no visible change. 1

cyclohexene (Bromine) (Acidified KMnO4) decolourised decolourised 1 [11]

Q15. Identification of acid by suitable method eg named indicator, named carbonate, specified reactive metal Ignore any reference to the smell of the ester. 1

with expected results Do not allow the use of any instrumental method eg i.r. or n.m.r.; must be a chemical test. 1

Identification of alcohol by suitable method eg oxidation by acidified potassium dichromate(VI) 1

with expected results 1 [4]

Q16. Compare spectrum of aldehyde with known spectrum of pentanal Must be a specific reference to a comparison. 1

Exact match Allow ‘fingerprint regions match exactly’. 1 [2]

Q17. (a) If 2 stage test for one compound, award no marks for that compound, eg no mark for ROH or RX to alkene then Br2 test. If reagent is wrong or missing, no mark for that test; if wrong but close/incomplete, lose reagent mark but can award for correct observation. In each test, penalise each example of wrong chemistry, eg AgClr2

Page 67 of 82 propan-1-ol

acidified potassium dichromate

sodium

Named acid + conc H2SO4

named acyl chloride

PCl5

M1 1

(orange) turns green

effervescence

Sweet smell

Sweet smell /misty fumes

Misty fumes

M2 1 propanal

add Tollens or Fehlings / Benedicts

acidified potassium dichromate

Bradys or 2,4-dnph if dichromate used for alcohol cannot be used for aldehyde

M3 1

Tollens: silver mirror or Fehlings/ Benedicts: red ppt

(orange) turns green

Yellow or orange ppt

M4 1 propanoic acid

Named carbonate/ hydrogencarbonate

water and UI (paper)

Page 68 of 82 Named alcohol + conc H2SO4

sodium or magnesium

PCl5 if sodium used for alcohol cannot be used for acid

M5 1

effervescence

orange/red

Sweet smell

effervescence

Misty fumes

if PCl5 used for alcohol cannot be used for acid

M6 1

1-chloro propane

NaOH then acidified AgNO3

AgNO3 If acidification missed after NaOH, no mark here but allow mark for observation

M7 1

white ppt

M8 1

(b) oxidation (of alcohol by oxygen in air)

M1 1

absorption at 1680 -1750 (due to C=O) Must refer to the spectrum

M2 1

comparison of polarity of molecules or correct imf statement: propanone is less polar OR propan-2-ol is more polar OR propanone has dipole-dipole forces OR propan-2-ol has hydrogen bonding

Page 69 of 82 M3 1

about attraction to stationary phase or solubility in moving phase Propan-2-ol has greater affinity for stationary phase or vice versa OR propanone is more soluble in solvent/moving phase or vice versa

M4 1 [12]

Q18. (a) (i) C 1

(ii) A 1

(iii) D 1

(iv) B 1

(b) M1 Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent) If M1, has no reagent or an incorrect reagent, CE=0 Ignore “acidified” For M1 penalise Br (or incorrect formula of other correct reagent), but mark on For M1, it must be a whole reagent and/or correct formulae

Either order If oxidation state given in name, it must be correct.

M2 cyclohexane OR A or the alkane: remains orange / red / yellow / brown / the same OR no reaction OR reference to colour going to cyclohexane layer For M2 credit “no change” Ignore “nothing” Ignore “nothing happens” Ignore “no observation”

M3 cyclohexene OR D or the alkene: decolourised / goes colourless / loses its colour For M3, ignore “goes clear”

Alternatives : potassium manganate(VII)

M1 KMnO4 in acid M2 purple M3 colourless

M1 KMnO4 in alkali / neutral M2 purple M3 brown solid

Give appropriate credit for the use of iodine and observations No credit for combustion observations 3

Page 70 of 82 (c) M1 acidified potassium or sodium dichromate For M1, it must be a whole reagent and/or correct formulae

+ OR eg H2SO4 / K2Cr2O7 OR H / K2Cr2O7

OR correct combination of formula and name If oxidation state given in name, it must be correct.

M2 oxidation OR oxidised OR redox Do not penalise incorrect attempt at formula if name is correct or vice versa

M3 secondary / 2o (alcohol)

Credit acidified potassium chromate(VI) / H2SO4 + K2CrO4 3

(d) M1 (free-) radical substitution (mechanism) M1 both words required

M2 Br2 2Br• Penalise absence of dot once only.

M3 Br• + CH4 •CH3 + HBr Penalise + or – charges every time

M4 Br2 + •CH3 CH3Br + Br• Accept dot anywhere on methyl radical Accept a correct termination step for 1 mark if neither M3 nor M4 are scored; otherwise ignore termination steps Mark independently

NB If Cl2 is used, penalise every time ( this may be for M2, M3 and M4) If cyclohexane is used, penalise every time (this may be for M3 and M4)

M5 Condition

ultra-violet / uv / sun light

OR high temperature

OR 125 °C ≤ T ≤ 600 °C

OR 400 K ≤ T ≤ 870 K For M5 ignore “heat” 5 [15]

Q19. (a) H OR hydrogen OR H• Ignore brackets ignore dot penalise + or – charge 1

Page 71 of 82 • • (b) CH3 OR methyl OR CH3 OR CH3 Ignore brackets ignore dot penalise + or – charge 1

• • C2H5 OR ethyl OR CH3CH2 OR C2H5 Ignore brackets ignore dot penalise + or – charge 1

CHO OR HCO OR COH OR H—C=O 1

(d) I A 1

II C 1

III D 1

IV B 1 [8]

Q20. (a) OH alcohols 1

(b) (i) 2.6

Ignore any group on RHS Must clearly indicate relevant two H on a C next to C=O

On LHS, penalise H or CH or CH2 or CH3 Ignore missing trailing bonds or attached R groups 1

(ii) 2.2

Ignore all groups on RHS Must clearly indicate relevant three H on C next to C=O Ignore missing trailing bonds or attached R group 1

(iii) 1.2

Page 72 of 82

Or in words: two equivalent CH3 groups Must clearly indicate two equivalent methyl groups.

Penalise attached H Ignore missing trailing bonds or attached R groups 1

(iv)

1 [5]

Q21. Test bromine (water) / iodine

Accept ‘Br2’ or ‘bromine in a named solvent’. Do not accept ‘Br’ Use of UV light, CE (lose next mark as well) 1

Observation orange / yellow / (red-)brown to colourless Must have correct reagent to score this mark.

For I2, allow red-brown / purple to colourless. 1 [2]

Q22. (a) (i) Green Ignore shades of green. 1

(ii) Excess acidified potassium dichromate(VI) 1

Reflux (for some time) 1

In the diagram credit should be given for • a vertical condenser Lose M3 and M4 for a distillation apparatus. 1

• an apparatus which would clearly work Do not allow this mark for a flask drawn on its own. Penalise diagrams where the apparatus is sealed. 1

Page 73 of 82 (iii) Distillation 1

Immediately (the reagents are mixed) 1

(b) Keep away from naked flames Allow heat with water-bath or heating mantle. If a list is given ignore eye protection, otherwise lose this mark. 1

(c) (i) Tollens’ or Fehling’s reagents Incorrect reagent(s) loses both marks. Accept mis-spellings if meaning is clear. 1

Silver mirror / red ppt. formed Accept ‘blue to red’ but not ‘red’ alone. 1

(ii) Sodium carbonate (solution) / Group II metal Allow indicator solutions with appropriate colours. Accept any named carbonate or hydrogen carbonate. 1

Effervescence / evolves a gas Accept ‘fizzes’. 1

(d) Propanoic acid If this mark is lost allow one mark if there is reference to stronger intermolecular forces in the named compound. Lose M1 and M3. 1

Contains hydrogen bonding 1

Some comparison with other compounds explaining that the intermolecular forces are stronger in propanoic acid 1 [15]

Q23. 1-chloropropane no visible change Accept ‘small amount of precipitate’ or ‘precipitate forms slowly’. 1

ethanoyl chloride white precipitate Accept ‘large amount of precipitate’ or ‘precipitate forms immediately’. 1 [2]

Page 74 of 82 Q24. (i) More absorption/less transmittance of infrared radiation by it/water vapour

OR broader absorption by OH

OR less absorption/more transmittance of infrared radiation by carbon dioxide Must be comparative This may be described and must not be contradictory Credit answers which refer correctly to “transmittance” (more absorption = less transmittance) 1

(ii) M1 CO2 contains C=O (stated like this or in words or strongly implied) OR is O=C=O

M2 depends on correct M1

OR expected absorption/peak (for C=O) is missing

OR expected absorption/peak (for C=O) is shifted to 2300 (cm–1)

OR asymmetric stretching is occurring (due to C=O) If M1 and M2 not scored, give one mark for either No absorption/peak at 1700 (cm–1)/1715 (cm–1) OR no absorption in the range 1680 – 1750 (cm–1) Ignore “carbon-oxygen bonds”, “C-O bonds” Ignore reference to other absorptions For M2 Allow “dip” OR “spike” OR “low transmittance” as alternatives for absorption. 2 [3]

Q25. (a) (i) 3-bromo-3-methylpentane ONLY Must be correct spelling but ignore hyphens and commas 1

(ii) Electrophilic addition (reaction) Both words needed Accept phonetic spelling 1

(iii) M1 Displayed formula of 2-bromo-3-methylpentane

Page 75 of 82

All the bonds must be drawn out but ignore bond angles

M2 Position(al) (isomerism) Do not forget to award this mark 2

(iv) Structure of (E)-3-methylpent-2-ene

The arrangement of groups around the double bond must be clear with the ethyl group attached in the correct order. Ignore bond angles.

Accept C2H5 for ethyl Be lenient on C ─ C bonds. The main issue here is whether they have drawn an (E) isomer. Accept “sticks” for C ─ H bonds and correct skeletal formula 1

(b) (i) M1 R is represented by Spectrum 2

M2 Spectrum 2 shows an infrared absorption/spike/dip/ trough/peak with any value(s)/range within the range 1620 to 1680 (cm–1) OR this range quoted/identified and this is due to C=C OR this information could be a correctly labelled absorption on the spectrum

OR Spectrum 1 does not have an infrared absorption in range 1620 to 1680 (cm–1) and does not contain C=C. Award M1 if it is obvious that they are referring to the second spectrum (or the bottom one) M2 depends on a correct M1 Ignore other correctly labelled peaks Ignore reference to “double bond” or “alkene” 2

(ii) Functional group (isomerism) 1

(iii) Cyclohexane

Methylcyclopentane etc.

Page 76 of 82 Named correctly Ignore structures and ignore numbers on the methyl group of methylcyclopentane 1 [9]

Q26. (a) OH acid (present in acid not in ester) Allow absorption at 2500–3000 cm–1 in acid. 1

(b) C=O or (absorption at) 1680–1750 cm–1 (present in acid not in alcohol) Allow correct distinction between 3230–3550 cm–1 for OH alcohol and 2500–3000 cm–1 for OH acid. 1

(Exact) match (with known spectrum) 1 [4]

Q27. (a) Fractional distillation (under reduced pressure) 1

(b) BaSO4 insoluble / remove by filtration Do not allow answers which refer to reaction rate 1

Q28. (a) Secondary OR 2° (alcohol); 1

(b) Spectrum is for butanone (or formula) or butan-2-one The explanation marks depend on correctly identifying butanone.

If butanone is correctly identified, award any two from

• (Strong) absorption / peak at approximately 1700 (cm–1) / 1710 (cm–1) / in the range 1680 – 1750 (cm–1) This needs to be stated.

• (Characteristic) absorption / peak for C=O (may be shown

Page 77 of 82 on the spectrum in the correct place).

• No absorption / peak in range 3230 to 3550 cm–1. 1

• No absorption / peak for an OH group. Look at the spectrum to see if anything is written on it that might gain credit. Allow the words “dip” OR “spike” OR “low transmittance” as alternatives for absorption. 2

Must have all bonds drawn out but ignore the bond angles 1 [5]

Q29. (a) Allow 1 mark each for any correctly drawn primary, secondary and tertiary alcohol of molecular formula C4H8O 3

Tertiary alcohol cannot be oxidised 1

(b) Region 1500–400 cm–1 1

exact match to spectrum of known compound 1

C D one alkene e.g. one cycloalkane e.g.

CH2=CHCH2CH2CH3

CH3–CH=CH–CH2CH3

(CH3)2C=CHCH3

H2C=C(CH3)CH2CH3 (1) etc

Page 78 of 82 E F CH3CH2CHO (1) CH3COCH3 (1) 6 [12]

Q30. (a) GLC or distillation 1

(b) C=O 1

(ii) 1

+• • C4H7ClO → + C2H4Cl 1

(d) (i) e.g. CDCl3 or CCl4 1

(ii) Si(CH3)4 1

(e) 0 and 3 1

(f)

(g) CH3CH2CH2COCl or (CH3)2CHCOCl 1 [10]

Q31. (a) X (O–H) (alcohols) penalise acid or missing “alcohol” 1

Y C=O allow carbonyl 1

Page 79 of 82

NOT acid 4

(b)

Allow conseq dibromocompounds following incorrect unbranched alkenes NOT allow dibromocompound consequent on a duplicate alkene NOT allow monobromocompounds if HBr added 3

6:3:1 either next to correct structure or to none 1

Allow a mark for identifying correct dibromocompound with three peaks even if integration ratio is wrong 1

if 6:3:1 missing or wrong, no marks for splitting

Only award a mark for splitting if it is clear which integration number it refers to

6 singlet or drawn 1

3 doublet or drawn 1

1 quartet/quadruplet or drawn 1 (max 10 marks) [16]

Q32. (a) (i)

or RCOCH3; (or description in words) (ignore trailing bonds) 1

Page 80 of 82 (ii) H3C—O or ROCH3;

(allow 1 if both (i) and (ii) give CH3- or H3C– only) 1

(iii) CH2CH2 or two adjacent methylene groups; 1

(iv)

CH3COCH2CH2OCH3; 1

(b) (i) OH in acids or (carboxylic) acid present

(ii)

(c)

+ + reagent K2Cr2O7 /H KMnO4 /H

Y no reaction no reaction

Z orange to green or purple to turns green colourless or turns colourless 5 [9]

Q33. B [1]

Q34. (a) R: O‑H (alcohols) (1) S: C=O or carbonyl (1) 2

(b) aldehyde (1) ‑CHO or RCHO (1) 1

(c) (i) Reason 1: TMS inert or non-toxic or volatile / easily removed Reason 2: single (intense) peak peak of 12 protons has 12 equivalent protons all protons in same environment

Page 81 of 82 OR peak / signal upfield of others highly shielded more shielded peak away from others or δ = 0 or low not solvent, not cheap any 2 reasons × (1)

(ii) Solvent: CDCl3 or CCl4 (NOT D2O) Reason: proton free (1) allow no hydrogens (atoms) NOT H+ / hydrogen ions 4

(d) (i) (1)

(ii) –OH (1)

(iii) –CH2–CH2– (1) 3

(e) (1) 1 [11]

Q35. D [1]

Page 82 of 82

Name: ______Periodicity exam pack

Class: ______

Date: ______

Time: 282 minutes

Marks: 270 marks

At minimum please complete:

Q3 – 8 marks

Q4 and Q7 - MC Comments: Q9 – 7 marks

Q 11 – 13 marks

Q14 - 10 marks

Page 1 of 54 Q1. This question is about atomic structure.

(a) Write the full electron configuration for each of the following species.

Cl−______

Fe2+______(2)

(b) Write an equation, including state symbols, to represent the process that occurs when the third ionisation energy of manganese is measured.

______

______(1)

Explain your answer.

______

______(3)

(d) A sample of nickel was analysed in a time of flight (TOF) mass spectrometer. The sample was ionised by electron impact ionisation. The spectrum produced showed three peaks with abundances as set out in the table.

m/z Abundance / % 58 61.0

60 29.1

61 9.9

Give the symbol, including mass number, of the ion that would reach the detector first in the sample.

Calculate the relative atomic mass of the nickel in the sample.

Page 2 of 54 Give your answer to one decimal place.

Symbol of ion ______

Relative atomic mass ______(3) (Total 9 marks)

Q2. Which of these elements has the highest second ionisation energy?

A Na

B Mg

C Ne

D Ar (Total 1 mark)

Q3. (a) Explain why the atomic radii of the elements decrease across Period 3 from sodium to chlorine.

______

______(2)

(b) Explain why the melting point of sulfur (S8) is greater than that of phosphorus (P4).

______

Page 3 of 54 ______

______(2)

______

______(2)

(d) Write an ionic equation for the reaction of phosphorus(V) oxide with an excess of sodium hydroxide solution.

______(1) (Total 7 marks)

Q4. Which elements are shown in increasing order of the stated property?

A Atomic radius: phosphorus, sulfur, chlorine.

B First ionisation energy: sodium, magnesium, aluminium.

C Electronegativity: sulfur, phosphorus, silicon.

D Melting point: argon, chlorine, sulfur. (Total 1 mark)

Q5. Which of the following is a correct statement about the trend in atomic radius across Period 3 of the Periodic Table?

radius increases because the atoms have more A electrons

B radius decreases because nuclear charge increases radius increases because shielding (screening) C increases radius decreases because shielding (screening) D decreases (Total 1 mark)

Page 4 of 54 Q6. Which element is in the f-block of the Periodic Table?

A Palladium

B Phosphorus

C Platinum

D Plutonium (Total 1 mark)

Q7. Which is the correct order of melting points of these Period 3 elements?

A phosphorus > sulfur > chlorine > argon

B argon > chlorine > phosphorus > sulfur

C sulfur > phosphorus > chlorine > argon

D chlorine > phosphorus > sulfur > argon (Total 1 mark)

Q8. Which is the correct classification for the element yttrium (Y)?

A s block

B p block

C d block

D f block (Total 1 mark)

Q9. This question is about Period 3 of the Periodic Table.

(a) Deduce which of Na+ and Mg2+ is the smaller ion. Explain your answer.

Smaller ion ______

Explanation ______

______

Page 5 of 54 ______

______(2)

(b) Write an equation to represent the process that occurs when the first ionisation energy for sodium is measured.

______(1)

Complete the graph by plotting the approximate first ionisation energy values for magnesium and sulfur.

Explain why the first ionisation energy of sulfur is different from that of phosphorus.

______

Page 6 of 54 ______

______(4) (Total 7 marks)

Q10. Which element is in the d-block of the Periodic Table?

A Selenium

B Antimony

C Tantalum

D Lead (Total 1 mark)

Q11. This question is about the periodicity of the Period 3 elements.

(a) State and explain the general trend in first ionisation energy across Period 3.

______

______(4)

(b) Give one example of an element which deviates from the general trend in first ionisation energy across Period 3.

Explain why this deviation occurs.

______

Page 7 of 54 ______

______

______(3)

Ionisation number 1 2 3 4 5 6 7 8

Ionisation energy / 1000 2260 3390 4540 6990 8490 27 100 31 700 kJ mol–1

Identify element Y.

Explain your answer using data from the table.

______

______(2)

(d) Identify the Period 3 element that has the highest melting point.

Explain your answer by reference to structure and bonding.

______

______(4) (Total 13 marks)

Q12.

Page 8 of 54 This question is about the elements in Period 3 of the Periodic Table.

(a) State the element in Period 3 that has the highest melting point. Explain your answer.

Element ______

Explanation ______

______

______(3)

(b) State the element in Period 3 that has the highest first ionisation energy. Explain your answer.

Element ______

Explanation ______

______

______(3)

______(1)

(d) Chlorine is a Period 3 element. Chlorine forms the molecules ClF3 and CCl2

(i) Use your understanding of electron pair repulsion to draw the shape of ClF3 and the shape of CCl2 Include any lone pairs of electrons that influence the shape.

Shape of ClF3 Shape of CCl2

Page 9 of 54 (2)

(ii) Name the shape of CCl2

______(1)

(iii) Write an equation to show the formation of one mole of ClF3 from its elements.

______(1) (Total 11 marks)

Q13. (a) Nickel is a metal with a high melting point.

(i) State the block in the Periodic Table that contains nickel.

______(1)

(ii) Explain, in terms of its structure and bonding, why nickel has a high melting point.

______

______(2)

(iii) Draw a labelled diagram to show the arrangement of particles in a crystal of nickel. In your answer, include at least six particles of each type.

(2)

(iv) Explain why nickel is ductile (can be stretched into wires).

______

______(1)

Page 10 of 54 (b) Nickel forms the compound nickel(II) chloride (NiCl2).

(i) Give the full electron configuration of the Ni2+ ion.

______(1)

(ii) Balance the following equation to show how anhydrous nickel(II) chloride can be obtained from the hydrated salt using SOCl2 Identify one substance that could react with both gaseous products.

...... NiCl2.6H2O(s) + ...... SOCl2(g) ...... NiCl2(s) + ...... SO2(g) + ...... HCl(g)

Substance ______(2) (Total 9 marks)

Q14. The elements in Period 2 show periodic trends.

(a) Identify the Period 2 element, from carbon to fluorine, that has the largest atomic radius. Explain your answer.

Element ______

Explanation ______

______

______(3)

(b) State the general trend in first ionisation energies from carbon to neon. Deduce the element that deviates from this trend and explain why this element deviates from the trend.

Trend ______

Element that deviates ______

Explanation ______

______

______(4)

(c) Write an equation, including state symbols, for the reaction that occurs when the first ionisation energy of carbon is measured.

Page 11 of 54 ______(1)

(d) Explain why the second ionisation energy of carbon is higher than the first ionisation energy of carbon.

______

______(1)

(e) Deduce the element in Period 2, from lithium to neon, that has the highest second ionisation energy.

______(1) (Total 10 marks)

Q15. The element rubidium exists as the isotopes 85Rb and 87Rb

(a) State the number of protons and the number of neutrons in an atom of the isotope 85Rb

Number of protons ______

Number of neutrons ______(2)

(b) (i) Explain how the gaseous atoms of rubidium are ionised in a mass spectrometer

______

______(2)

(ii) Write an equation, including state symbols, to show the process that occurs when the first ionisation energy of rubidium is measured.

______(1)

Page 12 of 54 Element sodium potassium rubidium

First ionisation 494 418 402 energy / kJ mol–1

State one reason why the first ionisation energy of rubidium is lower than the first ionisation energy of sodium.

______

______(1)

(d) (i) State the block of elements in the Periodic Table that contains rubidium.

______(1)

(ii) Deduce the full electron configuration of a rubidium atom.

______(1)

(e) A sample of rubidium contains the isotopes 85Rb and 87Rb only. The isotope 85Rb has an abundance 2.5 times greater than that of 87Rb

Calculate the relative atomic mass of rubidium in this sample. Give your answer to one decimal place.

______

______(3)

(f) By reference to the relevant part of the mass spectrometer, explain how the abundance of an isotope in a sample of rubidium is determined.

Name of relevant part ______

Explanation ______

______

______(2)

(g) Predict whether an atom of 88Sr will have an atomic radius that is larger than, smaller than or the same as the atomic radius of 87Rb. Explain your answer.

Page 13 of 54 Atomic radius of 88Sr compared to 87Rb ______

Explanation ______

______

______(3) (Total 16 marks)

Q16. Trends in physical properties occur across all Periods in the Periodic Table. This question is about trends in the Period 2 elements from lithium to nitrogen.

(a) Identify, from the Period 2 elements lithium to nitrogen, the element that has the largest atomic radius.

______(1)

(b) (i) State the general trend in first ionisation energies for the Period 2 elements lithium to nitrogen.

______(1)

(ii) Identify the element that deviates from this general trend, from lithium to nitrogen, and explain your answer.

Element ______

Explanation ______

______

(Extra space) ______

______(3)

First Second Third Fourth Fifth Sixth

Ionisation energy 1090 2350 4610 6220 37 800 47 000 / kJ mol-1

______(1)

(d) Draw a cross on the diagram to show the melting point of nitrogen.

Page 14 of 54

(1)

(e) Explain, in terms of structure and bonding, why the melting point of carbon is high.

______

(Extra space) ______

______

______(3) (Total 10 marks)

Q17. This question is about the first ionisation energies of some elements in the Periodic Table.

(a) Write an equation, including state symbols, to show the reaction that occurs when the first ionisation energy of lithium is measured.

______(1)

Page 15 of 54 (b) State and explain the general trend in first ionisation energies for the Period 3 elements aluminium to argon.

Trend ______

Explanation ______

______

(Extra space) ______

______(3)

State how selenium deviates from this general trend and explain your answer.

How selenium deviates from this trend ______

Explanation ______

______

(Extra space) ______(3)

(d) Suggest why the first ionisation energy of krypton is lower than the first ionisation energy of argon.

______

______(1)

(e) The table below gives the successive ionisation energies of an element.

First Second Third Fourth Fifth

Ionisation energy / kJ mol–1 590 1150 4940 6480 8120

Deduce the group in the Periodic Table that contains this element.

______(1)

(f) Identify the element that has a 5+ ion with an electron configuration of 1s2 2s2 2p6 3s2 3p6 3d10

Page 16 of 54 ______(1) (Total 10 marks)

Q18. Indium is in Group 3 in the Periodic Table and exists as a mixture of the isotopes 113In and 115In.

(a) Use your understanding of the Periodic Table to complete the electron configuration of indium.

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 ______(1)

(b) A sample of indium must be ionised before it can be analysed in a mass spectrometer.

(i) State what is used to ionise a sample of indium in a mass spectrometer.

______

______(1)

(ii) Write an equation, including state symbols, for the ionisation of indium that requires the minimum energy.

______(1)

(iii) State why more than the minimum energy is not used to ionise the sample of indium.

______

______(1)

(iv) Give two reasons why the sample of indium must be ionised.

Reason 1 ______

Reason 2 ______(2)

(c) A mass spectrum of a sample of indium showed two peaks at m/z = 113 and m/z = 115. The relative atomic mass of this sample of indium is 114.5

(i) Give the meaning of the term relative atomic mass.

______

Page 17 of 54 ______

______(2)

(ii) Use these data to calculate the ratio of the relative abundances of the two isotopes.

______

______(2)

(d) State and explain the difference, if any, between the chemical properties of the isotopes 113In and 115In

Difference in chemical properties ______

Explanation ______(2)

(e) Indium forms a compound X with hydrogen and oxygen. Compound X contains 69.2% indium and 1.8% hydrogen by mass. Calculate the empirical formula of compound X.

______

______(3) (Total 15 marks)

Q19. The following table gives the melting points of some elements in Period 3.

Element Na Al Si P S

Melting point / K 371 933 1680 317 392

(a) State the type of structure shown by a crystal of silicon. Explain why the melting point of silicon is very high.

______

Page 18 of 54 ______

______(3)

(b) State the type of structure shown by crystals of sulfur and phosphorus. Explain why the melting point of sulfur is higher than the melting point of phosphorus.

______

______(3)

(c) Draw a diagram to show how the particles are arranged in aluminium and explain why aluminium is malleable. (You should show a minimum of six aluminium particles arranged in two dimensions.)

______

______(3)

(d) Explain why the melting point of aluminium is higher than the melting point of sodium.

______

______(3) (Total 12 marks)

Q20. The following diagram shows the first ionisation energies of some Period 3 elements.

Page 19 of 54

(a) Draw a cross on the diagram to show the first ionisation energy of aluminium. (1)

(b) Write an equation to show the process that occurs when the first ionisation energy of aluminium is measured.

______(2)

(c) State which of the first, second or third ionisations of aluminium would produce an ion with the electron configuration 1s2 2s2 2p6 3s1

______(1)

(d) Explain why the value of the first ionisation energy of sulfur is less than the value of the first ionisation energy of phosphorus.

______

______(2)

(e) Identify the element in Period 2 that has the highest first ionisation energy and give its electron configuration.

Element ______

Electron configuration ______(2)

(f) State the trend in first ionisation energies in Group 2 from beryllium to barium. Explain your answer in terms of a suitable model of atomic structure.

Trend ______

Explanation ______

______

Page 20 of 54 ______

______(3) (Total 11 marks)

Q21. Ionisation energies provide evidence for the arrangement of electrons in atoms.

(a) Complete the electron configuration of the Mg+ ion.

1s2 ______(1)

(b) (i) State the meaning of the term first ionisation energy.

______

______(2)

(ii) Write an equation, including state symbols, to show the reaction that occurs when the second ionisation energy of magnesium is measured.

______(1)

(iii) Explain why the second ionisation energy of magnesium is greater than the first ionisation energy of magnesium.

______

______(1)

(iv) Use your understanding of electron arrangement to complete the table by suggesting a value for the third ionisation energy of magnesium.

First Second Third Fourth Fifth

Ionisation energies of 736 1450 10 500 13 629 magnesium / kJ mol–1

(1)

Trend ______

Page 21 of 54 Explanation ______

______

______(3)

(d) State how the element sulfur deviates from the general trend in first ionisation energies across Period 3. Explain your answer.

How sulfur deviates from the trend ______

______

Explanation ______

______

______(3)

(e) A general trend exists in the first ionisation energies of the Period 2 elements lithium to fluorine. Identify one element which deviates from this general trend.

______(1) (Total 13 marks)

Q22. This question is about the elements in Period 3 from Na to P

(a) (i) Explain the meaning of the term first ionisation energy.

______

______(2)

(ii) State and explain the general trend in first ionisation energies for the elements Na to P

Trend ______

Explanation ______

______

______(3)

(iii) State which one of the elements from Na to P deviates from this general trend and explain why this occurs.

Trend ______

Page 22 of 54 Explanation ______

______

______(3)

(b) State which one of the elements from Na to P has the highest melting point and explain your answer.

Element ______

Explanation ______

______

______(3) (Total 11 marks)

Q23. The elements phosphorus, sulfur, chlorine and argon are in the p block of the Periodic Table.

(a) State why these elements are classified as p block elements.

______(1)

(b) State the trend in atomic radius from phosphorus to chlorine and explain the trend.

Trend ______

Explanation ______

______

______(3)

______

______(3)

(d) In terms of atomic structure, explain why the van der Waals’ forces in liquid argon are very weak.

______

Page 23 of 54 ______

______(2) (Total 9 marks)

Q24. (a) Explain why certain elements in the Periodic Table are classified as p-block elements. Illustrate your answer with an example of a p-block element and give its electronic configuration. (3)

(b) Explain the meaning of the term periodicity as applied to the properties of rows of elements in the Periodic Table. Describe and explain the trends in atomic radius, in electronegativity and in conductivity for the elements sodium to argon. (13) (Total 16 marks)

Q25. (a) Complete the following table.

Particle Relative charge Relative mass

Proton

Neutron

Electron

(3)

(b) An atom of element Z has two more protons and two more neutrons than an atom of . Give the symbol, including mass number and atomic number, for this atom of Z.

______(2)

S 1s2 ______

S2– 1s2 ______(2)

(d) State the block in the Periodic Table in which sulphur is placed and explain your answer.

Block ______

Page 24 of 54 Explanation ______(2)

(e) Sodium sulphide, Na2S, is a high melting point solid which conducts electricity when molten. Carbon disulphide, CS2, is a liquid which does not conduct electricity.

(i) Deduce the type of bonding present in Na2S and that present in CS2

Bonding in Na2S ______

Bonding in CS2 ______

(ii) By reference to all the atoms involved explain, in terms of electrons, how Na2S is formed from its atoms.

______

(iii) Draw a diagram, including all the outer electrons, to represent the bonding present in CS2

(iv) When heated with steam, CS2 reacts to form hydrogen sulphide, H2S, and carbon dioxide. Write an equation for this reaction.

______(7) (Total 16 narks)

Q26. (a) (i) Complete the electronic configuration of aluminium.

1s2 ______

(ii) State the block in the Periodic Table to which aluminium belongs.

______(2)

(b) Describe the bonding in metals.

______

Page 25 of 54 ______

______(2)

______

______(3)

(d) Explain how metals conduct electricity.

______

______(2) (Total 9 marks)

Q27. (a) State the meaning of the term electronegativity.

______

______(2)

(b) State and explain the trend in electronegativity values across Period 3 from sodium to chlorine.

Trend ______

Explanation ______(3)

______

______(2)

(d) The diagram below shows the variation in first ionisation energy across Period 3.

Page 26 of 54

(i) What is the maximum number of electrons that can be accommodated in an s sub-level?

______

(ii) What evidence from the diagram supports your answer to part (d)(i)?

______

(iii) What evidence from the diagram supports the fact that the 3p sub-level is higher in energy than the 3s?

______

(iv) What evidence from the diagram supports the fact that no more than three unpaired electrons can be accommodated in the 3p sub-level?

______

______(5) (Total 12 marks)

Q28. (a) P and Q are oxides of Period 3 elements.

Oxide P is a solid with a high melting point. It does not conduct electricity when solid but does conduct when molten or when dissolved in water. Oxide P reacts with water forming a solution with a high pH.

Oxide Q is a colourless gas at room temperature. It dissolves in water to give a

Page 27 of 54 solution with a low pH.

(i) Identify P. State the type of bonding present in P and explain its electrical conductivity. Write an equation for the reaction of P with water.

(ii) Identify Q. State the type of bonding present in Q and explain why it is a gas at room temperature. Write an equation for the reaction of Q with water. (9)

(b) R is a hydroxide of a Period 3 element. It is insoluble in water but dissolves in both aqueous sodium hydroxide and aqueous sulphuric acid.

(i) Give the name used to describe this behaviour of the hydroxide.

(ii) Write equations for the reactions occurring.

(iii) Suggest why R is insoluble in water. (6) (Total 15 marks)

Q29. Which one of the following statements is correct?

A The first ionisation energies of the elements in Period 3 show a general decrease from sodium to chlorine.

B The electronegativities of Group 2 elements decrease from magnesium to barium.

C The strength of the intermolecular forces increases from hydrogen fluoride to hydrogen chloride.

D The ability of a halide ion to act as a reducing agent decreases from fluoride to iodide. (Total 1 mark)

Q30. (a) When aluminium is added to an aqueous solution of copper(II) chloride, CuCl2, copper metal and aluminium chloride, AlCl3, are formed. Write an equation to represent this reaction.

______(1)

(b) (i) State the general trend in the first ionisation energy of the Period 3 elements from Na to Ar.

______

(ii) State how, and explain why, the first ionisation energy of aluminium does not follow this general trend.

______

Page 28 of 54 ______(4)

(c) Give the equation, including state symbols, for the process which represents the second ionisation energy of aluminium.

______(1)

(d) State and explain the trend in the melting points of the Period 3 metals Na, Mg and Al.

Trend ______

Explanation ______

______

______(3) (Total 9 marks)

Q31. (a) State the meaning of the term first ionisation energy of an atom.

______

______(2)

(b) Complete the electron arrangement for the Mg2+ ion.

1s2 ______(1)

______(1)

(d) Write an equation to illustrate the process occurring when the second ionisation energy of magnesium is measured.

______(1)

(e) The Ne atom and the Mg2+ ion have the same number of electrons. Give two reasons why the first ionisation energy of neon is lower than the third ionisation energy of magnesium.

Reason 1 ______

Reason 2 ______(2)

(f) There is a general trend in the first ionisation energies of the Period 3 elements, Na –

Page 29 of 54 Ar

(i) State and explain this general trend.

Trend ______

Explanation ______

______

(ii) Explain why the first ionisation energy of sulphur is lower than would be predicted from the general trend.

______

______(5) (Total 12 marks)

Page 30 of 54 Mark schemes

Q1. (a) Cl− 1s22s22p63s23p6 1 Fe2+1s22s22p63s23p63d6 1 If [Ne] or [Ar] used then Max 1if both correct Ignore 4s0 Allow subscripts

(b) Mn2+ (g) Mn3+ (g) + e− 1 ⟶States symbols are required Allow Mn2+ (g) − e− Mn3+ (g) Negative charge needed on electron ⟶ (c) Al Mg then CE = 0 1 (Outer) electron in (3)p sublevel / orbital Not just level or shell 1 Higher in energy / further from the nucleus so easier to remove OWTTE Both required for M3 1 Ignore shielding

(d) 58Ni+ M1 needs mass and charge – allow subscripts 1 Ar= [(58 × 61.0) + (60 × 29.1) + (61 × 9.9)] / 100 1 Ar= 58.9 must be to 1dp 1 [9]

Q2. A [1]

Q3. (a) The number of protons increases (across the period) / nuclear charge increases 1

Therefore, the attraction between the nucleus and electrons increases Can only score M2 if M1 is correct 1

(b) S8 molecules are bigger than P4 molecules

Page 31 of 54 Allow sulfur molecules have bigger surface area and sulfur molecules have bigger Mr 1

Therefore, van der Waals / dispersion / London forces between molecules are stronger in sulfur 1

These O2– ions react with water forming OH– ions

2– – O + H2O 2OH scores M1 and M2 1

– 3- (d) P4O10 + 12OH 4PO4 + 6H2O 1 [7]

Q4. D [1]

Q5. B [1]

Q6. D [1]

Q7. C [1]

Q8. C [1]

Q9. (a) Mg(2+) or Magnesium Na+ CE=0 1

Because Mg2+ has more protons AND With the same shielding/screening/electron arrangement/number of electrons (or isoelectronic) Allow larger/stronger nuclear charge

Page 32 of 54 Ignore atomic radius 1

(b) Na(g) → Na+(g) + e− 1 for correct species and gas phase Allow e without charge Allow Na(g) – e− → Na+(g) Na(g) + e− → Na+(g) + 2e− 1

S between 800-1040 If S not lower than P on graph then M1 only If no plots on graph must state S below P to access M3 & M4 1

e− paired in (3)p orbital in S (owtte) Allow (3)p subshell/sublevel provided pair mentioned 1

Paired e− repel (so less energy needed to remove) 1 [7]

Q10. C [1]

Q11. (a) General increase If not increase then CE 1 Greater nuclear charge / more protons 1 Same shielding / electrons added to same shell Allow similar 1 Stronger attraction (from nucleus) for outer electron(s) Allow electron in outer shell 1

(b) Aluminium / Al (lower than Mg) CE if not Al or S 1 (Outer) electron in (3)p orbital / sub-shell (level) If 2p or 4p orbital lose M2 and M3 1 (3p) higher in energy Allow more shielded or weaker nuclear attraction M3 is dependent on M2 1 or

Page 33 of 54 Sulfur / S (lower than P) (Outer) electrons in (3)p orbital begin to pair Repel If 2p or 4p orbital lose M2 and M3 Allow 2 electrons in (3)p M3 is dependent on M2

(d) Silicon CE if not Si 1 Giant covalent structure / macromolecule 1 Covalent (bonds) Giant covalent scores M2 and M3 1 Many / strong (covalent bonds) or (covalent bonds) need lots of energy to break CE for M2-M4 if molecules / metallic / ionic / IMFs mentioned 1 [13]

Q12. (a) Silicon / Si If not silicon then CE = 0 / 3 1

covalent (bonds) M3 dependent on correct M2 1

Strong or many of the (covalent) bonds need to be broken / needs a lot of energy to break the (covalent) bonds Ignore hard to break 1

(b) Argon / Ar If not argon then CE = 0 / 3. But if Kr chosen, lose M1 and allow M2+M3 1

Large(st) number of protons / large(st) nuclear charge Ignore smallest atomic radius 1

Same amount of shielding / same number of shells / same number of energy levels Allow similar shielding 1

Page 34 of 54 (c) Chlorine / Cl 2 Not Cl2, Not CL, Not Cl 1

(d) (i)

Or any structure with 3 bonds and 2 lone pairs Ignore any angles shown 1

Or a structure with 2 bonds and 1 lone pair 1

(ii) Bent / v shape Ignore non-linear, angular and triangular Apply list principle 1

(iii) Cl2 + F2 ClF3 No multiples Ignore state symbols 1 [11]

Q13. (a) (i) d (block) OR D (block) Ignore transition metals / series. Do not allow any numbers in the answer. 1

(ii) Contains positive (metal) ions or protons or nuclei and delocalised / mobile / free / sea of electrons Ignore atoms. 1

Strong attraction between them or strong metallic bonds Allow ‘needs a lot of energy to break / overcome’ instead of ‘strong’. If strong attraction between incorrect particles, then CE = 0 / 2. If molecules / intermolecular forces / covalent bonding / ionic bonding mentioned then CE=0.

Page 35 of 54 1

(iii)

M1 is for regular arrangement of atoms / ions (min 6 metal particles). M2 for + sign in each metal atom / ion. Allow 2+ sign. 2

(iv) Layers / planes / sheets of atoms or ions can slide over one another QoL. 1

(b) (i) 1s2 2s2 2p6 3s2 3p6 3d8 (4s0) Only. 1

(ii) NiCl2.6H2O + 6 SOCl2 NiCl2 + 6 SO2 + 12 HCl Allow multiples. 1

NaOH / NH3 / CaCO3 / CaO Allow any name or formula of alkali or base. Allow water. 1 [9]

Q14. (a) Carbon / C If M1 incorrect, CE = 0 / 3 1

Fewest protons / smallest nuclear charge / least attraction between protons (in the nucleus) and electrons / weakest nuclear attraction to electrons Allow comparative answers. Allow converse answers for M2 1

Similar shielding Allow same shielding. 1

(b) Increase 1

Oxygen / O If not oxygen, then cannot score M2, M3 and M4 1

Paired electrons in a (2)p orbital If paired electrons in incorrect p orbital, lose M3 but can award M4

Page 36 of 54 1

(Paired electrons in a p orbital) repel 1

C(g) + e (−) → C+(g) + 2e (−)

C(g) − e (−) → C+(g) Ignore state symbols for electron. 1

(d) (More energy to) remove an electron from a (more) positive ion / cation Allow electron closer to the nucleus in the positive ion. 1

(e) Lithium / lithium / Li

If formula given, upper and lower case letters must be as shown. 1 [10]

Q15. (a) 37 These answers only. Allow answers in words. 1

48 Ignore any sum(s) shown to work out the answers. 1

(b) (i) Electron gun / high speed/high energy electrons Not just electrons. Not highly charged electrons. 1

Knock out electron(s) Remove an electron. 1

(ii) Rb(g) → Rb+(g) + e(–) OR Rb(g) + e(–) → Rb+(g) + 2e(–) OR Rb(g) - e(–) → Rb+(g) Ignore state symbols for electron. 1

(c) Rb is a bigger (atom) / e further from nucleus / electron lost from a higher energy level/ More shielding in Rb / less attraction of nucleus in Rb for outer

Page 37 of 54 electron / more shells Answer should refer to Rb not Rb molecule If converse stated it must be obvious it refers to Na Answer should be comparative. 1

(d) (i) s / block s / group s Only 1

(ii) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 Allow 3d10 before 4s2 Allow in any order. 1

(e) (85 × 2.5) + 87 ×1 3.5 M1 is for top line 1 1

= 85.6 Only 1

(58 × 5) + 87 ×2 7 M185Rb 71.4% and 87Rb 28.6% M2 divide by 100 1 1

85.6 M3 = 85.6 1

(f) Detector Mark independently Allow detection (plate). 1

Current / digital pulses / electrical signal related to abundance Not electrical charge. 1

(g) Smaller Chemical error if not smaller, CE = 0/3 If blank mark on. 1

Bigger nuclear charge / more protons in Sr Not bigger nucleus. 1

Page 38 of 54 Similar/same shielding QWC (Outer) electron entering same shell/sub shell/orbital/same number of shells. Do not allow incorrect orbital. 1 [16]

Q16. (a) Lithium / Li Penalise obvious capital I (second letter). 1

(b) (i) Increase / gets bigger Ignore exceptions to trend here even if wrong 1

(ii) Boron / B If not Boron, CE = 0/3 1

Electron removed from (2)p orbital /sub-shell / (2)p electrons removed If p orbital specified it must be 2p 1

Which is higher in energy (so more easily lost) / more shielded (so more easily lost) / further from nucleus 1

(d) Below Li

The cross should be placed on the diagram, on the column for nitrogen, below the level of the cross printed on the diagram for Lithium. 1

Page 39 of 54 (e) Macromolecular / giant molecular / giant atomic Allow giant covalent (molecule) = 2 1

Covalent bonds in the structure 1

Strong (covalent) bonds must be broken or overcome / (covalent) bonds need a lot of energy to break Ignore weakening / loosening bonds If ionic / metallic/molecular/ dipole dipole/ H bonds/ bonds between molecules, CE = 0/3 Ignore van der Waals forces Ignore hard to break 1 [10]

Q17. (a) Li(g) → Li+(g) + e-(g)

Li(g) - e-(g) → Li+(g)

Li(g) + e-(g) → Li+(g) + 2e- One mark for balanced equation with state symbols Charge and state on electron need not be shown 1

(b) Increases If trend wrong then CE = 0/3 for (b). If blank mark on. 1

Increasing nuclear charge / increasing no of protons Ignore effective with regard to nuclear charge 1

Same or similar shielding / same no of shells / electron (taken) from same (sub)shell / electron closer to the nucleus / smaller atomic radius 1

Paired electrons in a (4) p orbital If incorrect p orbital then M2 = 0 1

(Paired electrons) repel If shared pair of electrons M2 + M3 = 0 1

(d) Kr is a bigger atom / has more shells / more shielding in Kr / electron removed further from nucleus/ electron removed from a higher (principal or main) energy level

Page 40 of 54 CE if molecule mentioned Must be comparative answer QWC 1

(e) 2 / two / II 1

(f) Arsenic / As 1 [10]

Q18. (a) 4d10 5s2 5p1 in any order Allow subscripts for numbers Allow capitals 1

(b) (i) Using an electron gun/(beam of) high energy/fast moving electrons Ignore ‘knocks out an electron’ 1

(ii) In(g) + e– → In+(g) + 2e–

In(g) → In+(g) + e–

In(g) – e– → In+(g) The state symbols need not be present for the electron - but if they are they must be (g) No need to show charge on electron If I CE = 0 Ignore any equations using M 1

(iii) So no more than 1 electron is knocked out/so only one electron is knocked out/prevent further ionisation Allow stop 2+ and 3+/other ions being formed Not to get wrong m/z 1

(iv) Any two processes from

• Accelerate (owtte)

• Deflect (owtte)

• Detect (owtte) Ignore wrong causes of process 2 max

Page 41 of 54 1/12 mass of one atom of 12C 1

(Average) mass of one mole of atoms

1/12 mass of one mole of 12C

(Weighted) average mass of all the isotopes

1/12 mass of one atom of 12C

Average mass of an atom/isotope compared to C-12 on a scale in which an atom of C-12 has a mass of 12 Not average mass of 1 molecule Allow the wording Average mass of 1 atom of an element compared to 1/12 mass atom of 12C (or mass 1/12 atom of 12C) Allow if moles of atoms on both lines Accept answer in words Can have top line × 12 instead of bottom line ÷12 If atoms/moles mixed, max = 1

(ii) Allow idea that there are 4 × 0.5 divisions between 113 and 115 1

ratio (113:115) = 1:3 OR 25:75 OR 0.5:1.5 etc Correct answer scores M1 and M2 If 1:3 for In(115):In(113), max = 1 1

(d) None 1

Same no of electrons (in the outer shell)/same electron configuration) Ignore electrons determine chemical properties/ignore protons M2 dependent on M1 being correct 1

(e) 29.0%/29% O If no O calculated, allow M2 if In and H divided by the correct Ar 1

Page 42 of 54 or

0.603 1.8 1.81

1 3 3

EF = In H3O3

Allow In(OH)3 Do not allow last mark just for ratio 1:3:3

If InO3H3 given with no working then allow 3 marks If I not In, lose M3 1 [15]

Q19. (a) Macromolecular/giant covalent/giant molecular/giant atomic If IMF/H-bonds/Ionic/metallic CE = 0/3 covalent bond between molecules CE = 0/3 If giant unqualified M1 = 0 but mark on 1

Many/strong covalent bonds M2 and M3 can only be scored if covalent mentioned in answer Ignore metalloid and carbon Ignore bp 1

Bonds must be broken/overcome Ignore numbers of bonds and references to energy 1

(b) (Simple) molecular QoL Do not allow simple covalent for M1 Giant covalent/ionic/metallic, CE = 0 If breaking covalent bonds CE= 0/3 1

S bigger molecule (than P) or S8 and P4 references QoL

Allow more electrons in sulfur molecule or S8 Do not allow S is bigger then P

Allow S molecule has a bigger Mr Do not allow contradictions 1

So more/stronger van der Waals’ forces (to be broken or overcome) Not just more energy to break 1

Page 43 of 54 minimum of 2 rows Ignore e– Do not allow ring arrangements OR structures bonded with electrons 1

+ charge in each one (of 6) Allow +, (1+, 2+ or 3+) in ions/or in words 1

Rows/planes/sheets/layers (of atoms/ions) can slide (owtte) over one another M3 independent If ionic bonding/molecules/IMF/vdw/covalent, penalise M3 Ignore layers of electrons sliding 1

(d) Bigger charge (3+ compared to 1+) CE = 0 if molecules, ionic, covalent, IMF (Allow Al2+)

OR smaller atom/ion in Al/more protons/bigger nuclear charge 1

More free/delocalised electrons (in Al)/bigger sea of electrons in Al Accept 2 or 3 delocalised electrons compared to 1 in Na 1

Stronger metallic bonding/stronger (electrostatic) attraction between the (+) ions or nuclei and the (delocalised) electrons (or implied) Must be implied that the electrons are the delocalised ones not the electrons in the shells. Accept converse arguments 1 [12]

Q20. (a) Cross between the Na cross and the Mg cross 1

(b) Al(g) → Al+(g) + e– Al(g) – e– → Al+(g) Al(g) + e– → Al+(g) + 2e– One mark for state symbols consequential on getting equation correct. Electron does not have to have the – sign on it Ignore (g) if put as state symbol with e– but penalise state symbol mark if other state symbols on e– 2

Page 44 of 54 (d) Paired electrons in (3)p orbital Penalise wrong number If paired electrons repel allow M2 1

repel 1

(e) Neon/Ne No consequential marking from wrong element 1

1s22s22p6/[He}2s22p6 Allow capital s and p Allow subscript numbers 1

(f) Decreases CE if wrong 1

Atomic radius increases/electron removed further from nucleus or nuclear charge/electron in higher energy level/Atoms get larger/more shells Accept more repulsion between more electrons for M2 Mark is for distance from nucleus Must be comparative answers from M2 and M3 CE M2 and M3 if mention molecules Not more sub-shells 1

As group is descended more shielding 1 [11]

Q21. (a) 2s22p63s1 1s2 can be rewritten 2 2 2 2 1 Allow 2s 2px 2py 2pz 3s Allow subscripts and capitals 1

(b) (i) Energy/enthalpy (needed) to remove one mole of electrons from one mole of atoms/compounds/molecules/elements 1

Energy to form one mole of positive ions from one mole of atoms

Energy/enthalpy to remove one electron from one atom

In the gaseous state (to form 1 mol of gaseous ions) Energy given out loses M1

Page 45 of 54 M2 is dependent on a reasonable attempt at M1 Energy needed for this change X(g) → X+(g) + e(–) = 2 marks This equation alone scores one mark 1

(ii) Mg+(g) → Mg2+(g) + e(–) Mg+(g) + e(–) → Mg2+(g) + 2e(–) Mg+(g) – e(–) → Mg2+(g) Do not penalise MG Not equation with X 1

(iii) Electron being removed from a positive ion (therefore need more energy)/electron being removed is closer to the nucleus/Mg+ smaller (than Mg)/Mg+ more positive than Mg Allow from a + particle/species Not electron from a higher energy level/or higher sub-level More protons = 0 1

(iv) Range from 5000 to 9000 kJ mol–1 1

Bigger nuclear charge (from Na to Cl)/more protons QWC 1

electron (taken) from same (sub)shell/similar or same shielding/ electron closer to the nucleus/smaller atomic radius If no shielding = 0 Smaller ionic radius = 0 1

(d) Lower If not lower CE = 0/3 If blank mark on Allow does not increase 1

Two/pair of electrons in (3)p orbital or implied Not 2p 1

repel (each other) M3 dependent upon a reasonable attempt at M2 1

(e) Boron/B or oxygen/O/O2 1 [13]

Page 46 of 54 Q22. (a) (i) Energy/enthalpy (change)/∆H/ needed to remove 1 mole of electrons; Allow 1 electron Not heat alone 1

From 1 mol of gaseous atoms; From 1 gaseous atom Not mix and match moles and one electron. Allow 1 for balanced eq with ss 1

(ii) Increase; If blank mark on If incorrect CE = 0 1

Increasing nuclear charge/ increasing number of protons; Not increasing atomic number 1

Same or similar shielding /same number of shells or energy levels/ (atomic) radius decreases/electron closer to nucleus; Not same distance from nucleus. 1

(iii) Aluminium/Al; If incorrect CE = 0 1

Electron in higher energy /p or 3p orbital; Not 2p Ignore shielding 1

Less energy needed to lose electron/ electron more easily lost/ ionisation energy less; 1

(b) Silicon/Si; If incorrect CE = 0 If silicone, silica Si8, Si4 mark on. 1

Macromolecular/ Giant molecular or atomic or covalent; If IMFor ionic or metallic in Silicon then CE = 0 for explanation 1

Many or strong covalent bonds need to be broken/ lots of energy needed to break the covalent bonds; Not loosened bonds 1 [11]

Q23.

Page 47 of 54 (a) Outer electrons are in p orbitals 1

(b) decreases 1

Number of protons increases 1

Attracting outer electrons in the same shell (or similar shielding) 1

Therefore van der Waals’ forces between molecules are stronger 1

Therefore more energy needed to loosen forces between molecules 1

(d) Argon particles are single atoms with electrons closer to nucleus 1

Cannot easily be polarised (or electron cloud not easily distorted) 1 [9]

Q24. (a) Elements in the p block have their outer electron(s) in p orbital(s) or levels or sub-shells (1) example of element (1) correct electronic configuration (1) 3

(b) Pattern in the change in the properties of a row of elements (1) OR Trend in the properties of elements across a period

Repeated in the next row (1) OR element underneath (or in same group) has similar properties

atomic radius decreases across the row (1) CE if trend is wrong

number of protons increases (1) (or nuclear charge increases) more attraction for electrons in the same shell (1)

electronegativity increases across the row (1) number of protons increases (1) (or nuclear charge) atomic radius decreases (1) (or shielding remains the same or electrons in the same shell) more attraction for bonding or shared electrons (1)

conductivity decreases row (1)

Page 48 of 54 OR significant drop from Al to Si

Na–Al metals (1) OR metallic bonding or description of metallic bonding

Two of Si - Ar non metals (1) OR molecular or covalent

EITHER electrons free to move (or delocalised) in metals OR electrons unable to move in non-metals (1) 13 [16]

Q25. (a) Particle Relative charge Relative mass

Proton +1 or 1+ 1 (1)

Neutron 0 1 (not – 1) (1) or no charge/neutral/zero

Electron –1 or 1– 1/1800 to 1/2000 (1)

or negligible or zero or 5.0 × 10– 4 to 5.6 × 10– 4 if ‘g’ in mass column - wrong penalise once 3

(b) (1)(1) Allow numbers before or after Ar 2

S2–: 1s2 2s2 2p6 3s2 3p6 (1) If use subscript penalise once 2

(d) Block: p (1) Explanation: Highest energy or outer orbital is (3) p OR outer electron, valency electron in (3) p NOT 2p etc. 2

(e) (i) Bonding in Na2S: ionic (1) Bonding in CS2: covalent (1) ignore other words such as dative / polar / co-ordinate

Page 49 of 54 (ii) Clear indication of electron transfer from Na to S (1) 1 e– from each (of 2) Na atoms or 2 e– from 2 Na atoms (1) QoL correct English

(iii)

Correct covalent bonds (1) All correct including lone pairs (1) Allow all •s or all ×s M2 tied to M1 NOT separate e–s in S•- 2 l p

(iv) CS2 + 2H2O → CO2 + 2H2S (1) Ignore state symbols even if wrong 7 [16]

Q26. (a) (i) 1s2 2s2 2p6 3s2 3p1 (1) Allow subscripted electron numbers

(ii) p (block) (1) Allow upper or lower case ‘s’ and ‘p’ in (a)(i) and (a)(ii) 2

(b) Lattice of metal / +ve ions/ cations / atoms (1) Not +ve nuclei/centres Accept regular array/close packed/tightly packed/uniformly arranged

(Surrounded by) delocalised electrons (1) Note: Description as a ‘giant ionic lattice’ = CE 2

Smaller atoms / ions (1) Accept greater charge density for either M1 or M2

More delocalised electrons / e– in sea of e– / free e– (1)

Stronger attraction between ions and delocalised / free electrons etc. (1) Max 3 Note: ‘intermolecular attraction/ forces’ or covalent molecules = CE Accept stronger ‘electrostatic attraction’ if phrase prescribed elsewhere Ignore references to m/z values If Mg or Na compared to Al, rather than to each other, then:

Page 50 of 54 Max 2 Treat description that is effectively one for Ionisation Energy as a ‘contradiction’ 3

(d) (Delocalised) electrons (1)

Move / flow in a given direction (idea of moving non-randomly) or under the influence applied pd QoL mark (1) Allow ‘flow through metal’ Not: ‘Carry the charge’; ‘along the layers’; ‘move through the metal’ 2 [9]

Q27. (a) Ability (or power) of an atom to attract electron density (or electrons or ‑ve charge) (1) in a covalent bond (1) or shared pair If remove an electron lose first mark 2

(b) Trend: increases (1) Explanation: nuclear charge (number of protons) increases (1) electrons in same shell (1) OR similar shielding OR atoms similar size or smaller OR 1 mol of e- 3

(c) Heat / enthalpy / energy for removal of one electron (1) from a gaseous atom (1) can score in an equation must have first mark to score the second 2

(d) (i) 2 (1)

(ii) Two elements (or Na / Mg) before the drop (in energy) to Al (1)

(iii) ionisation energy of Al < that for Mg (1)

(iv) fall in energy from P to S (1) or discontinuity in trend

From Al to P there are 3 additional electrons (1) or three elements For second mark idea of block of 3 elements 5 [12]

Q28. (a) (i) Deductions:

Page 51 of 54 Ionic (1) Ions not free to move in the solid state (1) Ions free to move when molten or in aqueous solution (1) Identity of P: Na2O or sodium oxide (1) N.B. If a formula given this must be correct

Equation: Na2O + H2O → 2 NaOH (1) 5

(ii) Deductions:

Covalent Intermolecular forces are weak or van der Waals forces, or dipole-dipole N.B. Any answer including a reference to hydrogen bonding is incorrect

Identity of Q: SO2 or sulphur dioxide (1)

Equation: SO2 + H2O → H2 SO3(1)

NB Allow max one for SO3 4

(b) (i) Amphoteric (1)

(ii) Equation with NaOH

Al(OH)3 + NaOH → NaAl(OH)4 – – OR Al(OH)3(H2O)3 + OH → [Al(OH)4(H2O)2] + H2O – – OR Al(OH)3 + OH → [Al(OH)4]

R identified as Al(OH)3 or Al(OH)3(H2O)3 (1) A balanced equation (1) N.B. Allow equation with six co-ordinate Aluminium and up to six OH– ligands N.B. Allow equation mark if M(OH)3 given in a balanced equation

Equation with H2SO4

2Al(OH)3 + 3H2SO4 → Al2(SO4)3 + 6H2O

+ + OR Al(OH)3(H2O)3 + H → [Al(OH)2(H2O)4 + H2O NB Allow equations with six co-ordinate Aluminium and up to six H2O ligands NB Allow equation mark if M(OH)3 given in a balanced equation

Correct Al species as product (1) A balanced equation (1)

(iii) Large lattice energy or strong covalent bonds or ΔHsoln is very positive or ΔG is positive or sum of hydration energies less than covalent bond energies (1) 6 [15]

Page 52 of 54 Q29. B [1]

Q30. (a) 2Al + 3CuCl2 → 2AlCl3 + 3Cu; (accept multiples/fractions)

2Al+ 3Cu2+ → 2Al3+ + 3Cu; 1

(b) (i) increases; 1

(ii) lower than expected / lower than Mg / 1

less energy needed to ionise; e– removed from (3)p sub-level; 1

(‘e– removed’ may be implied)

of higher energy / further away from nucleus / shielded by 3s e–s; 1

(d) trend: increases; 1

more protons / higher charge on cation / more delocalised e– / smaller atomic/ionic radius; stronger attraction between (cat)ions and delocalised/free/mobile e– 1

stronger metallic bonding; 1 [9]

Q31. (a) enthalpy/energy change/required when an electron is removed/ knocked out / displaced/ to form a uni-positive ion (ignore ‘minimum’ energy) 1

from a gaseous atom (could get M2 from a correct equation here) (accept ‘Enthalpy/energy change for the process...’ followed by an appropriate equation, for both marks) (accept molar definitions) 1

Page 53 of 54 (b) 1s2 2s22p6 (accept capitals and subscripts) 1

(d) Mg+(g) → Mg2+(g) + e– or

Mg+(g) + e– → Mg2+(g) + 2e– or

Mg+(g) – e– → Mg2+(g) 1

(e) Mg2+ ion smaller than Ne atom / Mg2+ e– closer to nucleus (Not ‘atomic’ radius fo Mg2+) 1

Mg2+ has more protons than Ne / higher nuclear charge or e– is removed from a charged Mg2+ion / neutral neon atom (accept converse arguments) (If used ‘It’ or Mg/magnesium/Mg3+ etc. & 2 correct reasons, allow (1)) 1

(f) (i) trend: increases (if ‘decreases’, CE = 0/3) 1

Expln: more protons / increased proton number / increased nuclear charge (NOT increased atomic number) 1

same shell / same shielding / smaller size 1

(ii) QoL reference to the e– pair in the 3p sub-level (penalise if wrong shell, e.g. ‘2p’, quoted) 1

repulsion between the e–in this e–pair (if not stated, ‘e– pair’ must be clearly implied) (mark M4 and M5 separately) 1 [12]

Page 54 of 54

Name: ______REDOX exam pack

Class: ______

Date: ______

Time: 251 minutes

Marks: 216 marks

Comments:

Page 1 of 56 Q1. (a) In terms of electrons, what happens to an oxidising agent during a redox reaction?

______(1)

(b) Consider the following redox reaction.

+ + SO2(aq) + 2H2O(l) + 2Ag (aq) → 2Ag(s) + (aq) + 4H (aq)

(i) Identify the oxidising agent and the reducing agent in this reaction.

Oxidising agent ______

Reducing agent ______

(ii) Write a half-equation to show how sulphur dioxide is converted into sulphate ions in aqueous solution.

______(3)

(i) Write a half-equation for the oxidation of Fe2+ ions in this reaction.

______

(ii) Deduce the oxidation state of chlorine in ions.

______

(iii) Write a half-equation for the reduction of ions to Cl– ions in acidic conditions.

______

(iv) Hence, write an overall equation for the reaction.

______(4)

(d) Write an equation to show how sulphur is removed from impure iron obtained from the Blast Furnace. Identify the oxidising agent in this reaction.

Equation ______

Oxidising agent ______(2) (Total 10 marks)

Page 2 of 56 Q2. In which one of the following reactions does hydrogen not act as a reducing agent?

A H2 + Ca → CaH2

B 2H2 + O2 → 2H2O

C H2 + CH2=CH2 → CH3CH3

C 2H2 + CH3COCH3 → CH3CH2CH3 + H2O (Total 1 mark)

Q3. Chlorine and bromine are both oxidising agents.

(a) Define an oxidising agent in terms of electrons.

______(1)

(b) In aqueous solution, bromine oxidises sulphur dioxide, SO2, to sulphate ions,

(i) Deduce the oxidation state of sulphur in SO2 and in

SO2 ______

______

(ii) Deduce a half-equation for the reduction of bromine in aqueous solution.

______

(iii) Deduce a half-equation for the oxidation of SO2 in aqueous solution forming and H+ ions.

______

(iv) Use these two half-equations to construct an overall equation for the reaction between aqueous bromine and sulphur dioxide.

______(5)

(c) Write an equation for the reaction of chlorine with water. Below each of the chlorine-containing products in your equation, write the oxidation state of chlorine in that product.

______

______(3)

(d) Give a reason why chlorine is not formed when solid potassium chloride reacts with concentrated sulphuric acid.

Page 3 of 56 ______(1)

(e) Write an equation for the reaction between solid potassium chloride and concentrated sulphuric acid.

______(1)

(f) Solid potassium bromide undergoes a redox reaction with concentrated sulphuric acid.

(i) Give the oxidation product formed from potassium bromide.

______

(ii) Give the reduction product formed from sulphuric acid.

______(2) (Total 13 marks)

Q4. Photochromic glass contains silver ions and copper ions. A simplified version of a redox equilibrium is shown below. In bright sunlight the high energy u.v. light causes silver atoms to form and the glass darkens. When the intensity of the light is reduced the reaction is reversed and the glass lightens.

Cu+(s) + Ag+(s) Cu2+(s) + Ag(s)

clear glass dark glass

When the photochromic glass darkens

A the Ag+ ion is acting as an electron donor.

B the Cu+ ion is acting as a reducing agent.

C the Ag+ ion is oxidised.

D the Cu+ ion is reduced. (Total 1 mark)

Q5. (a) By referring to electrons, explain the meaning of the term oxidising agent.

______(1)

(b) For the element X in the ionic compound MX, explain the meaning of the term oxidation state.

______(1)

Page 4 of 56 (c) Complete the table below by deducing the oxidation state of each of the stated elements in the given ion or compound.

Oxidation state

Carbon in CO

Phosphorus in PCl

Nitrogen in Mg3N2

(3)

(d) In acidified aqueous solution, nitrate ions, NO , react with copper metal forming nitrogen monoxide, NO, and copper(II) ions.

(i) Write a half-equation for the oxidation of copper to copper(II) ions.

______

(ii) Write a half-equation for the reduction, in an acidified solution, of nitrate ions to nitrogen monoxide.

______

(iii) Write an overall equation for this reaction.

______(3) (Total 8 marks)

Q6. At high temperatures, nitrogen is oxidised by oxygen to form nitrogen monoxide in a reversible reaction as shown in the equation below.

ο –1 N2(g) + O2(g) 2NO(g) ∆H = +180 kJ mol

(a) In terms of electrons, give the meaning of the term oxidation.

______(1)

(b) State and explain the effect of an increase in pressure, and the effect of an increase in temperature, on the yield of nitrogen monoxide in the above equilibrium.

Effect of an increase in pressure on the yield ______

Explanation ______

______

Page 5 of 56 ______

Effect of an increase in temperature on the yield ______

Explanation ______

______

______(6)

(i) Deduce the oxidation state of nitrogen in NO and in NO

NO ______

(ii) Write a half-equation for the reduction of NO ions in acid solution to form nitrogen monoxide and water.

______

(iii) Write a half-equation for the oxidation of silver metal to Ag+(aq) ions.

______

(iv) Hence, deduce an overall equation for the reaction between silver metal and nitrate ions in acid solution.

______(5) (Total 12 marks)

Q7. Oxidation and reduction can de defined in terms of electron transfer.

(a) Define the term reduction in terms of electrons.

______(1)

(b) The oxide of nitrogen formed when copper reacts with nitric acid depends upon the concentration and the temperature of the acid. The reaction of copper with cold, dilute acid produces NO as indicated by the following equation.

+ 2+ 3Cu + 8H + → 3Cu + 4H2O + 2NO

In warm, concentrated acid, NO2 is formed.

Oxidation states can be used to understand electron transfer in these reactions.

Page 6 of 56 (i) Give the oxidation states of nitrogen in , NO and NO

Oxidation state in ______

Oxidation state in NO2 ______

Oxidation state in NO ______

(ii) Identify, as oxidation or reduction, the formation of NO2 from ions in the presence of H+ ions. Deduce the half-equation for the reaction.

NO from ______

Half-equation ______

(iii) Deduce the half-equation for the formation of NO2 from ions in the presence of H+ ions.

______

(iv) Deduce the overall equation for the reaction of copper with ions and H+ 2+ ions to produce Cu ions, NO2 and water.

______

______(8) (Total 9 marks)

Q8. This question is about Group 7 chemistry.

(a) Sea water is a major source of iodine. The iodine extracted from sea water is impure. It is purified in a two-stage process.

Stage 1 l2 + 2H2O + SO2 2Hl + H2SO4

Stage 2 2Hl + Cl2 l2 + 2HCl

(i) State the initial oxidation state and the final oxidation state of sulfur in Stage 1.

Oxidation state of S in SO2 ______

Oxidation state of S in H2SO4 ______(2)

(ii) State, in terms of electrons, what has happened to chlorine in Stage 2.

______

Page 7 of 56 (1)

(b) When concentrated sulfuric acid is added to potassium iodide, iodine is formed in the following redox equations.

...... KI + ...... H2SO4 ...... KHSO4 + ...... l2 + S + ...... H2O

8KI + 9H2SO4 8KHSO4 + 4l2 + H2S + 4H2O

(i) Balance the equation for the reaction that forms sulfur. (1)

(ii) Deduce the half-equation for the formation of iodine from iodide ions.

______(1)

(iii) Deduce the half-equation for the formation of hydrogen sulfide from concentrated sulfuric acid.

______(1)

(c) A yellow precipitate is formed when silver nitrate solution, acidified with dilute nitric acid, is added to an aqueous solution containing iodide ions.

(i) Write the simplest ionic equation for the formation of the yellow precipitate.

______(1)

(ii) State what is observed when concentrated ammonia solution is added to this yellow precipitate.

______

______(1)

(iii) State why the silver nitrate solution is acidified when testing for iodide ions.

______

______(1)

(iv) Explain why dilute hydrochloric acid is not used to acidify the silver nitrate solution in this test for iodide ions.

______

______(1)

Page 8 of 56 (d) Chlorine is toxic to humans. This toxicity does not prevent the large-scale use of chlorine in water treatment.

(i) Give one reason why water is treated with chlorine.

______

______(1)

(ii) Explain why the toxicity of chlorine does not prevent this use.

______

______(1)

(iii) Write an equation for the reaction of chlorine with cold water.

______(1)

(e) Give the formulas of the two different chlorine-containing compounds that are formed when chlorine reacts with cold, dilute, aqueous sodium hydroxide.

Formula 1 ______

Formula 2 ______(1) (Total 14 marks)

Q9. A sample of nitrogen dioxide gas (NO2) was prepared by the reaction of copper with concentrated nitric acid.

(a) (i) Balance the equation for the reaction of copper with concentrated nitric acid.

Cu + ...... HNO3 → Cu(NO3)2 + ...... NO2 + ...... H2O (1)

(ii) Give the oxidation state of nitrogen in each of the following compounds.

HNO3 ______

NO2 ______(2)

(iii) Deduce the half-equation for the conversion of HNO3 into NO2 in this reaction.

______(1)

(b) The following equilibrium is established between colourless dinitrogen tetraoxide gas (N2O4) and dark brown nitrogen dioxide gas.

Page 9 of 56 –1 N2O4(g) 2NO2(g) ΔH = 58 kJ mol

(i) Give two features of a reaction at equilibrium.

Feature 1 ______

______

Feature 2 ______

______

______(2)

(ii) Use Le Chatelier’s principle to explain why the mixture of gases becomes darker in colour when the mixture is heated at constant pressure.

______

______(2)

(iii) Use Le Chatelier’s principle to explain why the amount of NO2 decreases when the pressure is increased at constant temperature.

______

______(2) (Total 10 marks)

Q10. Hydrogen gas is used in the chemical industry.

Page 10 of 56 (a) Tungsten is extracted by passing hydrogen over heated tungsten oxide (WO3).

(i) State the role of the hydrogen in this reaction.

______(1)

(ii) Write an equation for this reaction.

______(1)

(iii) State one risk of using hydrogen gas in metal extractions.

______

______(1)

(b) Hydrogen is used to convert oleic acid into stearic acid as shown by the following equation.

+ H2 CH3(CH2)16COOH oleic acid stearic acid

(i) Use your knowledge of the chemistry of alkenes to deduce the type of reaction that has occurred in this conversion.

______(1)

(ii) State the type of stereoisomerism shown by oleic acid.

______(1)

(c) Hydrogen reacts with nitrogen in the Haber Process. The equation for the equilibrium that is established is shown below.

N2(g) + 3H2(g) 2NH3(g)

(i) State Le Chatelier’s principle.

______

______(1)

(ii) Use Le Chatelier’s principle to explain why an increase in the total pressure of this equilibrium results in an increase in the equilibrium yield of ammonia.

______

Page 11 of 56 ______

______

______(2)

(d) Hydrogen reacts with oxygen in an exothermic reaction as shown by the following equation.

–1 H2(g) + O2(g) → H2O(g) ∆H = –242 kJ mol

Use the information in the equation and the data in the following table to calculate a value for the bond enthalpy of the H–H bond.

O–H O=O

Mean bond enthalpy / kJ mol–1 + 463 + 496

______

______(3) (Total 11 marks)

Q11. Iodine reacts with concentrated nitric acid to produce nitrogen dioxide (NO2).

(a) (i) Give the oxidation state of iodine in each of the following.

I2 ______

HIO3 ______(2)

(ii) Complete the balancing of the following equation.

l2 + 10HNO3 ...... HIO3 + ...... NO2 + ...... H2O (1)

Page 12 of 56 – – + IO3 + 5e + 6H 3H2O +

l - + e–

Use these half-equations to deduce an overall ionic equation for the production of iodine by this process. Identify the oxidising agent.

Overall ionic equation

The oxidising agent ______(2)

(i) Identify the black solid.

______(1)

(ii) Deduce the half-equation for the formation of sulfur from concentrated sulfuric acid.

______(1)

(e) A yellow precipitate is formed when silver nitrate solution, acidified with dilute nitric acid, is added to an aqueous solution containing iodide ions.

(ii) Write the simplest ionic equation for the formation of the yellow precipitate.

Page 13 of 56 ______(1)

(ii) State what is observed when concentrated ammonia solution is added to this precipitate.

______

______(1)

(iii) State why the silver nitrate is acidified when testing for iodide ions.

______

______(1)

(f) Consider the following reaction in which iodide ions behave as reducing agents.

– – Cl2(aq) + 2I (aq) I2(aq) + 2Cl (aq)

(i) In terms of electrons, state the meaning of the term reducing agent.

______

______(1)

(ii) Write a half-equation for the conversion of chlorine into chloride ions.

______(1)

(iii) Suggest why iodide ions are stronger reducing agents than chloride ions.

______

(Extra space) ______

______(2) (Total 15 marks)

Q12. Antimony is a solid element that is used in industry. The method used for the extraction of antimony depends on the grade of the ore.

Page 14 of 56 (a) Antimony can be extracted by reacting scrap iron with low-grade ores that contain antimony sulfide (Sb2S3).

(i) Write an equation for the reaction of iron with antimony sulfide to form antimony and iron(II) sulfide.

______(1)

(ii) Write a half-equation to show what happens to the iron atoms in this reaction.

______(1)

(b) In the first stage of the extraction of antimony from a high-grade ore, antimony sulfide is roasted in air to convert it into antimony(III) oxide (Sb2O3) and sulfur dioxide.

(i) Write an equation for this reaction.

______(1)

(ii) Identify one substance that is manufactured directly from the sulfur dioxide formed in this reaction.

______(1)

(c) In the second stage of the extraction of antimony from a high-grade ore, antimony(III) oxide is reacted with carbon monoxide at high temperature.

(i) Use the standard enthalpies of formation in the table and the equation given below the table to calculate a value for the standard enthalpy change for this reaction.

Sb2O3(s) CO(g) Sb(I) CO2(g)

–1 ΔHf / kJ mol -705 -111 +20 -394

Sb2O3(s) + 3CO(g) 2Sb(I) + 3CO2(g)

______

______(3)

(ii) Suggest why the value for the standard enthalpy of formation of liquid antimony, given in the table above, is not zero.

______

Page 15 of 56 ______(1)

(iii) State the type of reaction that antimony(III) oxide has undergone in this reaction.

______(1)

(d) Deduce one reason why the method of extraction of antimony from a low-grade ore, described in part (a), is a low-cost process. Do not include the cost of the ore.

______

______(1) (Total 10 marks)

Q13. Vanadium is an important metal. Ferrovanadium, an alloy of iron and vanadium, is used to make a strong type of vanadium-steel. Pure vanadium is used in nuclear reactors.

(a) The table shows some standard enthalpy of formation data.

V2O5(s) CaO(s)

θ −1 ΔHf / kJ mol −1560 −635

In the oldest method of extraction of vanadium, V2O5 is reacted with calcium at a high temperature.

5Ca(s) + V2O5(s) 2V(s) + 5CaO(s)

Use data from the table and the equation to calculate the standard enthalpy change for this reaction.

State the type of reaction that V2O5 has undergone.

Suggest one major reason why this method of extracting vanadium is expensive, other than the cost of heating the reaction mixture.

______

Page 16 of 56 ______

______(5)

(b) Ferrovanadium is produced by the reaction of aluminium with a mixture of V2O5 and iron(III) oxide.

Write an equation for the reaction of aluminium with iron(III) oxide.

State the change in oxidation state of aluminium in this reaction.

______

______(2)

Write an equation for this reaction in which the only other product is HCl gas.

Identify two hazards in this process, other than the fact that it operates at a high temperature.

Deduce why this process produces pure vanadium, other than the fact that purified VCl2 is used.

______

______(4) (Total 11 marks)

Q14. The halogens are the elements in Group 7.

(a) The electronegativities of the halogens are shown in the table.

Halogen Fluorine Chlorine Bromine Iodine

Page 17 of 56 Electronegativity 4.0 3.0 2.8 2.5

Explain the trend in electronegativities shown by the halogens.

______

______(2)

(b) The halogens can all behave as oxidising agents in reactions.

(i) Explain, in terms of electron transfer, the meaning of the term oxidising agent.

______

______(1)

(ii) An equation for the reaction that takes place when chlorine gas is bubbled through aqueous potassium bromide is shown.

Cl2(g) + 2KBr(aq) → Br2(aq) + 2KCl(aq)

Explain, with reference to the oxidation states, why this is a redox reaction.

______

______(1)

(i) A sample of solid sodium iodide is reacted with concentrated sulfuric acid. A black solid forms and hydrogen sulfide gas is produced.

Write a half-equation for the reaction of sulfuric acid to form hydrogen sulfide.

______(1)

(ii) Write a half-equation for the formation of the black solid.

______(1)

(iii) Use your answers to parts (c) (i) and (c) (ii) to write an overall equation for the reaction of sodium iodide with concentrated sulfuric acid.

______(1)

Page 18 of 56 (iv) Give the role of sulfuric acid in its reaction with sodium iodide.

Tick (✔) one box.

Acid

Oxidising agent

Reducing agent

Electrophile

(1)

(v) Write an equation for the reaction of concentrated sulfuric acid with solid sodium fluoride.

______(1)

(vi) Suggest one reason why the reaction of sodium fluoride with concentrated sulfuric acid is different from the reaction with sodium iodide.

______(1)

(d) Chlorine reacts with water to form an equilibrium mixture containing hydrochloric acid and chloric(I) acid.

(i) Write an equation for the formation of this equilibrium mixture.

______(1)

______

______(2) (Total 13 marks)

Q15. Chlorine is an important industrial chemical.

(a) Chlorine is formed when KMnO4 reacts with hydrochloric acid. The ionic equation for this redox reaction is

+ − − 2+ 16H + 2MnO4 + 10Cl 2Mn + 8H2O + 5Cl2

Page 19 of 56 (i) Deduce the half-equation for the oxidation of chloride ions to chlorine.

______(1)

− (ii) Give the oxidation state of manganese in the MnO4 ion.

______(1)

− (iii) Deduce the half-equation for the reduction of the MnO4 ions in acidified solution to manganese(II) ions and water.

______(1)

(b) Chlorine behaves as an oxidising agent in the extraction of bromine from seawater. In this process, chlorine gas is bubbled through a solution containing bromide ions.

(i) Write the simplest ionic equation for the reaction of chlorine with bromide ions.

______(1)

(ii) Give one observation that would be made during this reaction.

______

______(1)

(iii) In terms of electrons, state the meaning of the term oxidising agent.

______

______(1)

Write an equation for this reaction. Give the oxidation state of chlorine in the chlorine-containing species that is formed.

Equation

______

Oxidation state of chlorine in the species formed ______(2)

(d) Explain why chlorine has a lower boiling point than bromine.

______

Page 20 of 56 ______

______

______(2) (Total 10 marks)

Q16. Refer to the unbalanced equation below when answering this question.

K2Cr2O7 + 3H2C2O4 + _H2SO4 → Cr2(SO4)3 + _H2O + 6CO2 + K2SO4

What is the reducing agent in this reaction?

+ A H

2− B C2O4

+ C K

2− D Cr2O7

(Total 1 mark)

Q17. Refer to the unbalanced equation below when answering this question.

K2Cr2O7 + 3H2C2O4 + _H2SO4 → Cr2(SO4)3 + _H2O + 6CO2 + K2SO4

In the balanced equation the mole ratio for sulfuric acid to water is

A 1 : 4

B 1 : 2

C 4 : 7

D 4 : 9 (Total 1 mark)

Q18. A student oxidised a solution of hydrochloric acid with a few drops of sodium chlorate(l) solution. The reaction mixture effervesced and turned pale green. The gas formed bleached universal indicator paper.

(a) Write a half-equation for the oxidation of chloride ions.

Page 21 of 56 ______(1)

(b) Write a half-equation for the reduction of chlorate(l) ions to chlorine in acidic conditions.

______(1)

(d) A solution of sodium chlorate(l) was added to a colourless solution of potassium iodide. Suggest what is observed.

Explain the reaction that leads to this observation.

______

______(3) (Total 6 marks)

Q19. Which species contains an element with an oxidation state of +4?

+ A NO2

− B ClO3

C H2SO3

D PCl5

(Total 1 mark)

Q20. Iodide ions are present in seawater but at very low concentrations. Certain types of seaweed are able to extract and concentrate iodide ions in their cells up to about 3% by mass. This seaweed could be a source of the element iodine (I2).

Page 22 of 56 The following is an account of a method that was used to extract I2 from Laminaria seaweed. The solvent tetrachloromethane (CCl4) is no longer used because it is very toxic.

A. Collect and dry some seaweed. Heat it very strongly in a crucible until a small quantity of ash is formed. B. Add distilled or deionised water to the cooled ash in a beaker. Boil the suspension for 5 minutes. Allow to cool. C. Filter the suspension. D. Gradually add dilute sulfuric acid to the filtrate until the solution is acidic. E. Add hydrogen peroxide solution. A brown solution will be formed. F. Transfer the solution to a separating funnel. G. Add CCl4 to the funnel. It forms a separate organic layer. This organic layer changes from a colourless liquid to a purple solution. H. Add the organic layer to an evaporating basin and place this in a fume cupboard. Grey-black crystals of iodine will form as the solvent evaporates.

(a) In Step A of the method, explain how it could have been confirmed that the decomposition of the seaweed was complete.

______

______(2)

(b) The suspension was filtered in Step C. Suggest an advantage of using vacuum filtration for this part of the method.

______

______(1)

(c) Describe how, in Step D, the solution could have been tested to show when it became acidic. Your method should not contaminate the solution.

______

______(2)

(d) Write an overall equation showing the oxidation of iodide ions to iodine in Step E using hydrogen peroxide solution in acidic conditions. (No oxygen is evolved in this reaction.)

______

______(1)

(e) A diagram of a separating funnel is shown below.

Page 23 of 56

Aqueous solutions and tetrachloromethane are immiscible. When added to the separating funnel they form two layers as shown in the diagram. Prolonged shaking of the mixture allows iodine (dissolved in the aqueous layer) to pass into the tetrachloromethane layer. The densities of some liquids are shown in the table.

Filtrate from Concentrate Liquid H2O CCl4 Step C d H2SO4

Density / g cm–3 1.0 1.2 1.6 1.8

Explain briefly whether the upper layer or the lower layer in the separating funnel is likely to show a purple colouration after Step G.

______

______(1)

(f) The iodine in the separating funnel quickly establishes an equilibrium after shaking the contents. The concentrations of iodine in the aqueous layer and in the CCl4 layer become constant. This is shown by the relationship

A sample of Laminaria seaweed, mass 56.4 g, was processed by the method given. After Step H, 1.673 g of iodine remained in the evaporating basin. The volume of each layer was 50.0 cm3. The seaweed contains 3.00% iodine by mass.

Calculate the value of K from these data. Show your working.

______

______(3)

(g) It has been suggested that cyclohexene could be used to extract the iodine from the aqueous layer. Explain why this would not be a suitable solvent.

Page 24 of 56 ______

______

______(2)

(h) The iodine produced at the end of Step H is impure and needs to be recrystallised from a suitable inert solvent. Explain the essential feature to consider when choosing a suitable inert solvent for this recrystallisation.

______

______(2) (Total 14 marks)

Q21. In which reaction is hydrogen acting as an oxidising agent?

A Cl2 + H2 2HCl

B (CH3)2CO + H2 (CH3)2CHOH

2 2 3 C N + 3H 2NH

D 2Na + H2 2NaH (Total 1 mark)

Q22. Sodium bromate(V) is a primary standard. This means that its solution can be used to check the concentration of other solutions.

(a) The half-equations for the reaction between bromate(V) ions and thiosulfate ions in the presence of acid are

2– 2– – 2S2O3 → S4O6 + 2e

– + – – BrO3 + 6H + 6e → Br + 3H2O

Use these half-equations to deduce an overall equation for this reaction.

______

Page 25 of 56 (1)

(b) A laboratory technician decided to use a 5.00 × 10–3 mol dm–3 solution of sodium bromate(V) to check the concentration of a sodium thiosulfate solution that was labelled as 1.00 × 10–3 mol dm–3. The sodium bromate(V) solution was placed in the burette and 25.0 cm3 of the sodium thiosulfate solution was pipetted into a conical flask.

Use the concentration of the sodium thiosulfate solution to calculate the expected titre value in this experiment. Show your working.

______

______(2)

Suggest one change to the experimental procedure in part (b) that would enable you to calculate a more accurate value for the concentration of the sodium thiosulfate solution.

______

______(1) (Total 4 marks)

Q23. In which reaction is the metal oxidised?

2+ – 2 A 2Cu + 4I 2CuI + I

3+ – 2+ B [Fe(H2O)6] + Cl [Fe(H2O)5(Cl)] + H2O

2– 2+ – C [CoCl4] + 6H2O [Co(H2O)6] + 4Cl

D Mg + S MgS (Total 1 mark)

Q24. Which of these is a redox reaction?

Page 26 of 56 A CaO + SiO2 CaSiO3

⟶ B H2SO4 + Na2O Na2SO4 + H2O ⟶ C NaBr + H2SO4 NaHSO4 + HBr ⟶ D Mg + S MgS ⟶ (Total 1 mark)

Q25. Which substance is not produced in a redox reaction when solid sodium iodide reacts with concentrated sulfuric acid?

A H2S

B HI

SO2 C

I2 D (Total 1 mark)

Q26. Which of the following shows chlorine in its correct oxidation states in the compounds shown?

HCl KClO3 HClO

A −1 +3 +1

B +1 −5 −1

C −1 +5 +1

D +1 +5 −1 (Total 1 mark)

Q27. This question is about the element iodine and its compounds.

(a) Iodine is in Group 7 of the Periodic Table.

Complete the electron configuration of an iodine atom.

[Kr] ______(1)

(b) Part of the structure of an iodine crystal is shown in the diagram.

Page 27 of 56

Use your knowledge of structure and bonding to explain why the melting point of iodine is low (113.5 °C) and why that of hydrogen iodide is very low (–50.8 °C). (6)

______

______(1)

(d) Deduce an equation for the formation of hydrogen iodide from its elements.

______(1)

(e) The triiodide ion is formed when an iodine molecule is bonded to an iodide ion.

What is the formula of ammonium triiodide?

Tick (✔) one box.

NH3I3

NH3I4

NH4I

NH4I3

(1)

− (f) Draw the shape of the IF3 molecule and the shape of the IF4 ion. Include any lone pairs of electrons that influence each shape.

Page 28 of 56 (2)

(g) Deduce the oxidation state of iodine in the following species.

Ba(IO3)2 ______

− [H4IO6] ______(2) (Total 14 marks)

Q28. Which of these species is the best reducing agent?

Cl2 A

− B Cl

I2 C

− D I

(Total 1 mark)

Q29. V2O5 can be used as a catalyst in the Contact Process.

Which is a step in the Contact Process in which the vanadium is oxidised?

A SO2 + V2O5 SO3 + 2VO2

⟶ B SO3 + 2VO2 SO2 + V2O5

C ⟶ 2VO2 + O2 V2O5

D ⟶ V2O5 2VO2 + O2

⟶ (Total 1 mark)

Q30. Which of these shows nitrogen in its correct oxidation states in the compounds given?

NH3 N2O HNO2

A +3 −1 +5

B −3 +1 +3

C −3 +1 −5

Page 29 of 56 D +3 −1 −3 (Total 1 mark)

Q31. Which species is not produced by a redox reaction between solid sodium iodide and concentrated sulfuric acid?

A Na2SO4

B H2S

C S

D SO2

(Total 1 mark)

Q32. Which of these is not a redox reaction?

A Cu2O + H2SO4 CuSO4 + Cu + H2O ⟶ B MgO + 2HCl MgCl2 + H2O ⟶ C SnCl2 + HgCl2 Hg + SnCl4

⟶ D MnO2 + 4HCl MnCl2 + 2H2O + Cl2

⟶ (Total 1 mark)

Q33. When an acidified solution of sodium nitrite (NaNO2) is added to aqueous potassium iodide, iodine and nitrogen monoxide (NO) are formed.

(a) Give the oxidation state of nitrogen in the following species.

− NO2 ______

NO______(2)

− (b) Write a half-equation for the conversion of NO2 in an acidic solution into NO

______(1)

− (c) Write a half-equation for the conversion of I into I2

______(1)

Page 30 of 56 − − (d) Write an overall ionic equation for the reaction of NO2 in an acidic solution with I

______(1)

− − (e) State the role of NO2 in the reaction with I

______(1)

(f) In aqueous solution, nitrite ions react with acidified chlorate(V) ions according to the equation

− − + − 2ClO3 + 5NO2 + 2H Cl2 + 5NO3 + H2O

25.0 cm3 sample of an aqueous solution ⟶of sodium nitrite required 27.40 cm3 of a 0.0200 mol dm−3 solution of potassium chlorate(V) for complete reaction.

Calculate the concentration, in g dm−3, of sodium nitrite in the sample.

Concentration of sodium nitrite ______g dm−3 (4) (Total 10 marks)

Q34. For many years, swimming pool water has been treated with chlorine gas. The chlorine is added to kill any harmful bacteria unintentionally introduced by swimmers. Pool managers are required to check that the chlorine concentration is high enough to kill the bacteria without being a health hazard to the swimmers.

When chlorine reacts with water in the absence of sunlight, the chlorine is both oxidised and reduced and an equilibrium is established.

(a) Write an equation for this equilibrium.

For each chlorine-containing species in the equation, write the oxidation state of chlorine below the species.

______

______(2)

(b) The pool manager maintains the water at a pH slightly greater than 7.0

Explain how this affects the equilibrium established when chlorine is added to water.

______

Page 31 of 56 ______

______

______(2)

______

______(2) (Total 6 marks)

Q35. Which one of the following is not a redox reaction?

+ − A Br2 + SO2 + 2H2O → SO + 4H + 2Br

B SnCl2 + HgCl2 → Hg + SnCl4

C Cu2O + H2SO4 → CuSO4 + Cu + H2O

+ D 2CrO + 2H → Cr2O + H2O (Total 1 mark)

Page 32 of 56 Mark schemes

Q1. (a) gains electrons (1) or accepts/takes electrons Allow an electron or just ‘gains’ or reduction is gain of electrons, but NOT OILRIG even if stated Do not allow mention of electron pair(s) 1

(b) (i) Oxidising agent: Ag+ (1) (or Ag I)

VI Reducing agent: SO2 (1) (or S , not sulphur)

2– + – + – (ii) SO2 + 2H2O → SO4 + 4H + 2e (1) (or H2SO4 + 2H + 2e ) allow e i.e. no charge penalise E– once only allow –e– on LHS 3

(ii) 5 (1) (or V or +5)

– + – – (iii) ClO3 + 6H + 6e → Cl + 3H2O (1)

– + 2+ – 3+ (iv) ClO3 + 6H + 6Fe → Cl + 3H2O +6Fe (1) Mark parts (i) to (iv) independently 4

(d) Equation: Mg + S → MgS (1) allow FeS + Mg → MgS + Fe allow Ca

Oxidising agent: S (1) Only award mark if first answer given unless no first answer then can allow 2 [10]

Q2. A [1]

Q3. (a) Gains electrons (or removes electrons) 1

(b) (i) +4 1

Page 33 of 56 1

– – (ii) Br2 + 2e → 2Br 1

+ – (iii) SO2 + 2H2O → 4H + + 2e 1

– + (iv) Br2 + SO2 + 2H2O → 2Br + 4H + 1

+ – (c) Cl2 + H2O → H + Cl + HOCl 1

Chloride: –1 1

Chlorate(I): +1 1

(d) Chloride ions cannot reduce sulphuric acid (Or chloride ions are weak reducing agents Or sulphuric acid is not a strong enough oxidising agent Or sulphuric acid is a weaker oxidising agent than chlorine) 1

(e) KCl + H2SO4 → HCl + KHSO4

(Allow 2KCl + H2SO4 → 2HCl + K2SO4) 1

(f) (i) Bromine 1

(ii) Sulphur dioxide 1 [13]

Q4. B [1]

Q5. (a) Accepts electrons 1

(b) Charge on the ion (or element or atom) 1

+5 1

–3 1

Page 34 of 56 (d) (i) Cu– → Cu2+ + 2e– 1

(ii) 1

(iii) 1 [8]

Q6. (a) removal/loss of electrons 1

(b) no change 1

equal number of gaseous moles on either side 1

both sides affected equally 1

increases 1

equilibrium moves to lower the temperature/oppose the change 1

endothermic reaction favoured /forward reaction is endothermic 1

– + – (ii) NO3 + 4H + 3e → NO +2H2O 1

(iii) Ag → Ag+ + e– 1

– + + (iv) NO3 + 4H + 3Ag → NO + 2H2O + 3Ag 1 [12]

Q7. (a) Gain of electrons 1

(b) (i) (+)5 or V or N5+ 1

(+)4 or IV or N4+ 1

(+)2 or II or N2+

Page 35 of 56 1

(ii) Reduction 1

+ – (–) 4H + NO3 + 3e → NO + 2H2O 1

+ – (–) (iii) 2H + NO3 + e → NO2 + H2O 1

+ – 2+ (iv) Cu + 4H + 2 NO3 → Cu + 2H2O + 2NO2

species 1

balanced If electrons included, mark CE if these are not balanced 1 [9]

Q8. (a) (i) M1 (+) 4 OR IV

M2 (+) 6 OR VI 2

(ii) It / Chlorine has gained / accepted electron(s)

− − Correctly balanced half-equation eg Cl2 + 2e 2Cl Credit 1 or 2 electrons but not lone pair. The idea of ‘reduction’ alone is not enough. 1

(b) (i) 6KI + 7H2SO4 6KHSO4 + 3I2 + S + 4H2O 1

− − (ii) 2I I2 + 2e

− − 8I 4I2 + 8e Ignore charge on the electron unless incorrect. Or multiples. Credit the electrons being subtracted on the LHS. Ignore state symbols. 1

+ − (iii) H2SO4 + 8H + 8e H2S + 4H2O

2− + – SO4 + 10H + 8e H2S + 4H2O Ignore charge on the electron unless incorrect. Or multiples.

Page 36 of 56 Credit the electrons being subtracted on the RHS. Ignore state symbols. 1

(ii) The precipitate / solid / it does not dissolve / is insoluble / remains

OR a white / cream / yellow solid / precipitate

OR stays the same

OR no (visible / observable) change

OR no effect / no reaction Ignore ‘nothing (happens)’. Ignore ‘no observation’. 1

(iii) The silver nitrate is acidified to

• react with / remove (an)ions that would interfere with the test Credit a correct reference to ions that give a ‘false positive’.

• remove (other) ions that react with the silver nitrate If only the formula of the ion is given, it must be correct.

• react with / remove carbonate / hydroxide / sulfite (ions) Ignore ‘sulfate’. 1

(d) (i) Any one from Ignore ‘to clean water’.

• to sterilise / disinfect water Ignore ‘water purification’ and ‘germs’.

• to destroy / kill microorganisms / bacteria / microbes / pathogens Credit ‘remove bacteria etc’ / prevent algae. 1

(ii) The (health) benefit outweighs the risk

Page 37 of 56 OR

a clear statement that once it has done its job, little of it remains

used in (very) dilute concentrations / small amounts / low doses 1

(iii) Cl2 + H2O HClO + HCl

+ − − Cl2 + H2O 2H + ClO + Cl

2Cl2 + 2H2O 4HCl + O2 Credit HOCl or ClOH Or multiples. Credit other ionic or mixed representations. Ignore state symbols. 1

(e) In either order - Both required for one mark only Credit correct ionic formulae.

NaClO (OR NaOCl) and NaCl Give credit for answers in equations unless contradicted. 1 [14]

Q9.

(a) (i) Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O Or multiples Ignore state symbols 1

(ii) M1 HNO3 (+) 5

M2 NO2 (+) 4 Ignore working out M1 Credit (V) M2 Credit (IV) 2

+ – (iii) HNO3 + H + e → NO2 + H2O

– + – NO3 + 2H + e → NO2 + H2O Or multiples Ignore state symbols

Page 38 of 56 Ignore charge on the electron unless incorrect and accept loss of electron on the RHS 1

(b) (i) In either order

M1 Concentration(s) (of reactants and products) remain(s) constant / stay(s) the same / remain(s) the same / do(es) not change

M2 Forward rate = Reverse / backward rate For M1 accept [ ] for concentration NOT “equal concentrations” and NOT “concentration(s) is/are the same” NOT “amount” Ignore “dynamic” and ignore “speed” Ignore “closed system” It is possible to score both marks under the heading of a single feature 2

(ii) M1

The (forward) reaction / to the right is endothermic or takes in / absorbs heat

The reverse reaction / to the left is exothermic or gives out / releases heat

M2 depends on correct M1 and must refer to temperature/heat

The equilibrium shifts / moves left to right to oppose the increase in temperature M2 depends on a correct statement for M1 For M2, the equilibrium shifts/moves to absorb the heat OR to lower the temperature OR to cool the reaction 2

(iii) M1 refers to number of moles

There are fewer moles (of gas) on the left OR more moles (of gas) on the right. OR there is one mole (of gas) on the left and 2 moles on the right.

M2 depends on correct M1 and must refer to pressure The equilibrium shifts / moves right to left to oppose the increase in pressure M2 depends on a correct statement for M1 For M2, the equilibrium shifts/moves to lower the pressure. 2 [10]

Page 39 of 56 Q10. (a) (i) Reducing agent

Reduce(s) (WO3/tungsten oxide)

electron donor

to remove oxygen (from WO3/tungsten oxide or to form water); 1

(ii) WO3 + 3H2 → W + 3H2O Or multiples 1

(iii) One from

H2 is

• explosive

• flammable or inflammable

• easily ignited Ignore reference to pressure or temperature 1

(b) (i) Addition Ignore “electrophilic” Penalise “nucleophilic addition”

(catalytic) hydrogenation

Reduction 1

(ii) Geometric(al)

cis/trans OR E Z OR E/Z 1

(c) (i) (If any factor is changed which affects an equilibrium), the position of equilibrium will shift/move/change/respond/act so as to oppose the change.

(When a system/reaction in equilibrium is disturbed), the

Page 40 of 56 equilibrium shifts/moves in a direction which tends to reduce the disturbance A variety of wording will be seen here and the key part is the last phrase and must refer to movement of the equilibrium. QoL 1

(ii) M1 – Statement of number of moles/molecules There are more moles/molecules (of gas) on the left/of reactants

fewer moles/molecules (of gas) on the right./products

there are 4 moles/molecules (of gas) on the left and 2 moles/ molecules on the right. Ignore “volumes” for M1 Mark independently

M2 – Explanation of response/movement in terms of pressure Increase in pressure is opposed (or words to that effect)

pressure is lowered by a shift in the equilibrium (from left) to right/favours forward reaction. 2

(d) ΣB(reactants) – ΣB(products) = ΔH (M1)

Sum of bonds broken – Sum of bonds formed = ΔH (M1)

B(H–H) + ½B(O=O) – 2B(O–H) = – 242 (M1)

B(H–H) = – 242 – ½(+496) + 2(+463) (this scores M1 and M2)

B(H–H) = (+)436 (kJ mol–1) (M3)

Award 1 mark for – 436

Candidates may use a cycle and gain full marks. M1 could stand alone Award full marks for correct answer. Ignore units. Two marks can score with an arithmetic error in the working. 3 [11]

Q11. (a) (i) M1 0

M2 (+) 5

Page 41 of 56 Accept Roman V for M2 2

(ii) I2 + 10HNO3 2HIO3 + 10NO2 + 4H2O Accept multiples 1

– + – (b) M1 IO3 + 6H + 5I 3I2 + 3H2O For M1, ignore state symbols Credit multiples

Accept 2½I2 + ½I2 as alternative to 3I2 Electrons must be cancelled

– M2 NaIO3 OR IO3 OR iodate ions OR iodate(V) ions etc. For M2 Do not penalise an incorrect name for the correct oxidising agent that is written in addition to the formula.

Accept “the iodine in iodate ions” but NOT “iodine” alone Accept “the iodine / I in iodate ions” but NOT “iodine” alone 2

+ – (ii) H2SO4 + 6H + 6e S + 4H2O Ignore state symbols

2– – SO4 + 8H+ + 6e S + 4H2O Credit multiples Do not penalise absence of charge on the electron 1

(d) hydrogen sulfide

OR H2S

OR hydrogen sulphide 1

(e) (i) Ag+ + I – AgI ONLY Ignore state symbols No multiples 1

(ii) The (yellow) precipitate / solid / it does not dissolve / is insoluble ignore “nothing (happens)”

OR turns to a white solid ignore “no observation”

OR stays the same

OR no (visible/ observable) change

OR no effect / no reaction 1

Page 42 of 56 (iii) The silver nitrate is acidified to

• react with / remove (an)ions that would interfere with the test Ignore reference to “false positive”

• remove (other) ions that react with the silver nitrate

• react with / remove carbonate / hydroxide / sulfite (ions) If only the formula of the ion is given, it must be correct 1

(f) (i) An electron donor Penalise “electron pair donor”

OR (readily) donates / loses / releases / gives (away) electron(s) Penalise “loss of electrons” alone Accept “electron donator” 1

– – (ii) Cl2 + 2e 2Cl Ignore state symbols Do not penalise absence of charge on electron – – Credit Cl2 2Cl – 2e Credit multiples 1

M1 Relative size of ions CE=0 for the clip if “iodine ions / chlorine ions” QoL

Iodide ions / they are larger /have more electron levels(shells) (than chloride ions) / larger atomic / ionic radius CE=0 for the clip if “iodide ions are bigger molecules / atoms” QoL

OR electron to be lost/outer shell/level (of the iodide ion) is further the nucleus

OR iodide ion(s) / they have greater / more shielding Insist on iodide ions in M1 and M2 or the use of it / they / them, in the correct context (or chloride ions in the converse argument)

OR converse for chloride ion

M2 Strength of attraction for electron(s) Must be comparative in both M1 and M2

Page 43 of 56 The electron(s) lost /outer shell/level electron from (an) iodide ion(s) less strongly held by the nucleus compared with that lost from a chloride ion

OR converse for a chloride ion 2 [15]

Q12. (a) (i) 3Fe + Sb2S3 3FeS + 2Sb Or multiples. Ignore state symbols. 1

(ii) Fe Fe2+ + 2e− Ignore charge on the electron unless incorrect. Or multiples. Credit the electrons being subtracted on the LHS. Ignore state symbols. 1

(b) (i) Sb2S3 + 4.5O2 Sb2O3 + 3SO2 Or multiples. Ignore state symbols. 1

(ii) SO3 or sulfur trioxide / sulfur (VI) oxide Credit also the following ONLY.

H2SO4 or sulfuric acid. OR

Gypsum / CaSO4 or plaster of Paris. 1

M1 ∆Hr = Ʃ∆Hf(products) − Ʃ∆Hf(reactants)

OR a correct cycle of balanced equations / correct numbers of moles Credit 1 mark for +104 (kJ mol−1).

M2 = 2(+20) + 3(−394) − (−705) − 3(−111)

= 40 −1182 + 705 + 333

= −1142 − (−1038)

(This also scores M1)

M3 = −104 (kJ mol−1)

(Award 1 mark ONLY for + 104) For other incorrect or incomplete answers, proceed as follows: • Check for an arithmetic error (AE), which is either

Page 44 of 56 a transposition error or an incorrect multiplication; this would score 2 marks. • If no AE, check for a correct method; this requires either a correct cycle with 3CO, 2Sb and 3CO2 OR a clear statement of M1 which could be in words and scores only M1. 3

(ii) It / Sb is not in its standard state

Standard state (for Sb) is solid / (s)

(Sb) liquid is not its standard state Credit a correct definition of standard state as an alternative to the words ‘standard state’. QoL 1

(iii) Reduction OR reduced OR redox 1

(d) Low-grade ore extraction / it

• uses (cheap) scrap / waste iron / steel

• is a single-step process

uses / requires less / low(er) energy Ignore references to temperature / heat or labour or technology. 1 [10]

Q13. (a) M1 (could be scored by a correct mathematical expression) M1 ΔH = ΣΔHf (products) − ΣΔHf (reactants) OR a correct cycle of balanced equations

M2 = 5(−635) − (−1560)

= − 3175 + 1560

(This also scores M1)

M3 = − 1615 (kJ mol−1) Award 1 mark ONLY for (+) 1615 Correct answer to the calculation gains all of M1, M2 and M3 Credit 1 mark for(+) 1615 (kJ mol−1) For other incorrect or incomplete answers, proceed as follows • check for an arithmetic error (AE), which is either a transposition error or an incorrect multiplication; this would score 2 marks (M1 and M2)

Page 45 of 56 • If no AE, check for a correct method; this requires either a correct cycle with V2O5 and 5CaO OR a clear statement of M1 which could be in words and scores only M1

M4 Type of reaction is • reduction • redox • (or accept) V2O5 / it / V(V) has been reduced In M4 not “vanadium / V is reduced”

M5 Major reason for expense of extraction − the answer must be about calcium

Calcium is produced / extracted by electrolysis OR calcium is expensive to extract OR calcium extraction uses electricity OR calcium extraction uses large amount of energy OR calcium is a (very) reactive metal / reacts with water or air OR calcium needs to be extracted / does not occur native QoL Accept calcium is expensive “to produce” but not “to source, to get, to obtain, to buy” etc. In M5 it is neither enough to say that calcium is “expensive” nor that calcium “must be purified” 5

(b) M1 2Al + Fe2O3 2Fe + Al2O3 Ignore state symbols Credit multiples of the equation

M2 (Change in oxidation state) 0 to (+)3 OR (changed by) +3 In M2 if an explanation is given it must be correct and unambiguous 2

M2 and M3 Two hazards in either order • HCl / hydrogen chloride / hydrochloric acid is acidic / corrosive / toxic / poisonous • Explosion risk with hydrogen (gas) OR H2 is flammable For M2 / M3 there must be reference to hydrogen; it is not enough to refer simply to an explosion risk For M2 / M3 with HCl hazard, require reference to acid(ic) / corrosive / toxic only

M4 The only other product / the HCl is easily / readily removed / lost / separated because it is a gas OR will escape (or this idea strongly implied) as a gas

Page 46 of 56 OR vanadium / it is the only solid product (and is easily separated) OR vanadium / it is a solid and the other product / HCl is a gas In M4 it is not enough to state simply that HCl is a gas, since this is in the question. 4 [11]

Q14. (a) Increasing atomic radius / shielding / number of shells / size (down group) or reverse argument NOT ‘molecules’ 1

Decreasing attraction of nucleus/protons for shared (electron) pair / bond electrons NOT if attraction for single electron implied 1

(b) (i) Electron acceptor / species that accepts electrons / species that gains electrons NOT electron pair NOT just ‘gain of electrons’ 1

+ (-) (c) (i) H2SO4 + 8H + 8e → H2S + 4H2O

2- + (-) ALLOW SO4 + 10H + 8e → H2S + 4H2O ALLOW fractions/multiples IGNORE state symbols 1

– (-) (ii) 2I → I2 + 2e ALLOW fractions/multiples IGNORE state symbols

- (-) ALLOW 2I - 2e →I2 1

+ - (iii) H2SO4 + 8H + 8I → H2S + 4H2O + 4I2 ALLOW

H2SO4 + 8HI → H2S + 4H2O + 4I2

2- + SO4 + 2H + 8HI → H2S + 4H2O + 4I2

2- + - SO4 + 10H + 8I → H2S + 4H2O+4I2

- - 9H2SO4 + 8I → H2S + 4H2O + 4I2 +8HSO4

Page 47 of 56 9H2SO4 + 8NaI → H2S + 4H2O + 4I2 + 8NaHSO4

+ + H2SO4 + 8H + 8NaI → H2S + 4H2O + 4I2 + 8Na

- 2- 5H2SO4 + 8I → H2S+4H2O + 4I2 + 4SO4

5H2SO4 + 8NaI → H2S + 4H2O + 4I2 + 4Na2SO4 1

(iv) ‘Oxidising agent’ box ticked 1

(v) H2SO4 + 2NaF → Na2SO4 + 2HF OR

H2SO4 + NaF → NaHSO4 + HF 1

+ - - (d) (i) Cl2 + H2O 2H + Cl + ClO /HCl + HOCl

ALLOW⇌ → for 1 ⇌ (ii) Equilibrium shifts/moves left 1

(Producing) chlorine (which) is toxic/poisonous Mark independently 1 [13]

Q15. − − (a) (i) 2Cl Cl2 + 2e Ignore state symbols Credit loss of electrons from LHS Credit multiples Do not penalise absence of charge on electron 1

(ii) +7 OR 7 OR VII OR +VII Allow Mn+7 and 7+ 1

− + − 2+ (iii) MnO4 + 8H + 5e Mn + 4H2O Ignore state symbols Credit loss of electrons from RHS Credit multiples

Page 48 of 56 Do not penalise absence of charge on electron 1

− − (b) (i) Cl2 + 2Br 2Cl + Br2

− − Cl2 + Br Cl + Br2 One of these two equations only Ignore state symbols 1

(iii) (Chlorine) gains electron(s) / takes electron(s) / accepts electron(s) (from the bromide ions)

(Chlorine) causes another species (Br−) to lose electron(s) Penalise “electron pair acceptor” Not simply “causes loss of electrons” 1

(4H+ + 4Cl−)

(d) M1 The relative size (of the molecules / atoms)

Chlorine is smaller than bromine OR has fewer electrons / electron shells For M1 ignore whether it refers to molecules or atoms.

OR It is smaller / It has a smaller atomic radius / it is a smaller molecule / atom (or converse) CE=0 for the clip for reference to (halide) ions or incorrect statements about relative size

Ignore molecular mass and Mr

M2 How size of the intermolecular force affects energy needed Ignore shielding

Page 49 of 56 The forces between chlorine / Cl2 molecules are weaker (than the forces between bromine / Br2 molecules) (or converse for bromine) OR chlorine / Cl2 has weaker / fewer / less (VdW) intermolecular forces / forces between molecules (or converse for bromine) QoL in M2 for clear reference to the difference in size of the force between molecules. Reference to Van der Waals forces alone is not enough. Penalise M2 if (covalent) bonds are broken 2 [10]

Q16. B [1]

Q17. C [1]

Q18.

− (−) (a) 2Cl → Cl2 + 2e

− (−) Allow 2Cl − 2e → Cl2 Allow correct equation forming ClO− but not Cl+ 1

− + − (b) 2ClO + 4H + 2e → Cl2 + 2H2O Allow HClO in correctly balanced equation 1

− − + (c) ClO + Cl + 2H → Cl2 + H2O

allow HClO + HCl + → Cl2 + H2O 1

(d) Goes brown (or shades of brown) Allow black ppt/solid but NOT black solution or purple 1

− Due to iodine or I3 Correct ½ equation scores M2 and M3 1

Because I− oxidised 1 [6]

Q19. C [1]

Page 50 of 56 Q20. (a) Reheat the sample at least once. Heat to constant mass gains both marks. 1

Mass of ash should not have changed. Mark independently. 1

(b) Vacuum filtration is quicker / saves time Allow ‘easier to wash residue to extract all iodide ions’. 1

(c) Use indicator (paper) on a withdrawn sample / place a pH probe into the solution If any indicator (including paper) is used directly on the solution lose this mark but then mark on. 1

Keep testing until paper shows acidity / until pH drops below 7. Indicator does not need to be specified but if it is then correct colour must be quoted. 1

– + (d) 2I + H2O2 + 2H → I2 + 2H2O – – Do not accept 2l + H2O2 → I2 + 2OH as reaction conditions are acidic. Accept multiples and fractions. Ignore state symbols. 1

(e) Lower layer – as it will be the denser CCl4 Mark is for correct identification and correct reasoning. 1

(f) Iodine in seaweed = 56.4 × (3/100) = 1.692 g 1

Iodine left in aqueous layer = 1.692 – 1.673 = 0.0190 g 1

K = (1.673/(253.8 × 0.05)) / (0.0190/(253.8 × 0.05)) = 88.1 Neither 253.8 nor 0.05 have to appear in working since they cancel. Accept 88 1

(g) It would react with the iodine Allow (electrophilic) addition OR forms 1,2 – diiodocyclohexane OR addition across a double bond for both marks. 1

It is unsaturated 1

(h) Solubility (of the iodine in the solvent) is high when hot and low when cold 1

Page 51 of 56 (Therefore, on cooling a solution,) a significant quantity of crystals appear 1 [14]

Q21. D [1]

Q22. 2– – + 2– – (a) 6S2O3 + BrO3 + 6H → 3S4O6 + Br + 3H2O Check the formulae and charges carefully and penalise any transcription errors. Allow multiples and fractions. Ignore state symbols. 1

(b) Mol of thio = 25.0 × 0.00100 / 1000 = 2.50 × 10−5 and Mol of bromate(V) = (1/6) × 2.5 x 10−5 = 4.17 × 10−6 If equation in Q5a is wrong, mark consequentially. 1

Vol of bromate(V) = (4.17 × 10−6 / 0.005) × 1000 = 0.83 cm3 Lose this mark if (correct) unit of volume not given. Do not penalise precision. 1

Q23. D [1]

Q24. D [1]

Q25. B [1]

Q26. C [1]

Q27.

Page 52 of 56 (a) [Kr] 5s2 4d105p5 1

(b) This question is marked using levels of response. Refer to the Mark Scheme Instructions for Examiners for guidance on how to mark this question.

Level 3 All stages are covered and the explanation of each stage is correct and complete.

Answer communicates the whole explanation coherently and shows a logical progression from stage 1 to stage 2 and then stage 3. 5-6 marks

Level 2 All stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies OR two stages are covered and the explanations are generally correct and virtually complete.

Answer is mainly coherent and shows a progression through the stages. Some steps in each stage may be out of order and incomplete. 3-4 marks

Level 1 Two stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies, OR only one stage is covered but the explanation is generally correct and virtually complete.

Answer includes some isolated statements, but these are not presented in a logical order or show confused reasoning. 1-2 marks

Level 0 Insufficient correct chemistry to warrant a mark. 0 marks Indicative Chemistry content Stage 1

I2 is molecular. HI is molecular. Stage 2 IMF hold the molecules together. There are weak IMF forces hence the melting point is low in both substances.

I2 bigger molecule than HI so I2 has more electrons. Stage 3

Therefore stronger van der Waals between molecules in I2 that need more energy to break causing the melting point to be higher. HI also shows permanent dipole-dipole attraction between molecules but these forces are less than the vdW forces in iodine. 6

(d) HI

⟶ Page 53 of 56 Allow multiples 1

(e) NH4I3 1

(f) Allow any shape with 3 bond pairs and 2 lone pairs 1

Allow any shape with 4 bond pairs and 2 lone pairs (e.g. lone pairs in equatorial positions) 1

(g) +5 1

+7 1 [14]

Q28. D [1]

Q29. C [1]

Q30. B [1]

Q31. A

Page 54 of 56 [1]

Q32. B [1]

Q33. − (a) NO2 +3 or III or 3 or 3+ 1 NO +2 or II or 2 or 2+ 1

− − + (b) NO2 + e + 2H NO + H2O (OR double) 1 ⟶ − − (c) 2I I2 + 2e (OR half) 1 ⟶ − + (d) 2NO2− + 2I + 4H I2 + 2NO + 2H2O 1 ⟶ (e) Oxidising agent Allow to accept / gain electrons Allow Oxidant Do not allow accept / gain pairs of electrons Do not allow Oxidise 1

− −4 (f) Mol ClO3 = 0.02 × = 5.48 × 10 1

− −3 Mol NO2 = (0.02 × ) = 1.37 × 10 ) 1

− − [NO2 ] = mol NO2 /( ) −3 [NaNO2] = 0.0548 moldm 1 −3 Conc NaNO2 = (0.0548) × 69.0 = 3.78 gdm 1 Minimum 2 sf [10]

Q34. (a) Cl2 + H2O HOCl + HCl Allow the products shown as ions. 1

Cl2 = 0, HOCl = +1 and HCl = −1 1 mark for all three oxidation states correct. Allow a reaction arrow in this equation. Oxidation states must match the species 1

Page 55 of 56 (b) Hydroxide / alkali ions react with the acids Mark independently 1

Equilibrium moves to the right 1

The health benefits outweigh the risks 1 [6]

Q35. D [1]

Page 56 of 56 Year 1 Practical Questions

Q1.This question is about a white solid, MHCO3, that dissolves in water and reacts with hydrochloric acid to give a salt.

MHCO3 + HCl → MCl + H2O + CO2

A student was asked to design an experiment to determine a value for the Mr of MHCO3. 3 The student dissolved 1464 mg of MHCO3 in water and made the solution up to 250 cm . 25.0 cm3 samples of the solution were titrated with 0.102 mol dm−3 hydrochloric acid. The results are shown in the table.

Rough 1 2 3 Initial burette 0.00 10.00 19.50 29.25 reading / cm3 Final burette 10.00 19.50 29.25 38.90 reading / cm3 Titre / cm3 10.00 9.50 9.75 9.65

(a) Calculate the mean titre and use this to determine the amount, in moles, of HCl that 3 reacted with 25.0 cm of the MHCO3 solution.

......

...... (3)

3 (b) Calculate the amount, in moles, of MHCO3 in 250 cm of the solution. Then calculate the experimental value for the Mr of MHCO3. Give your answer to the appropriate number of significant figures.

......

...... (3)

Page 1 experiment.

Using the same apparatus, suggest how the procedure could be improved to reduce the percentage uncertainty in using the burette.

Justify your suggested improvement.

Suggestion ......

......

Justification ......

......

...... (2)

(d) Another student is required to make up 250 cm3 of an aqueous solution that contains a known mass of MHCO3. The student is provided with a sample bottle containing the MHCO3.

Describe the method, including apparatus and practical details, that the student should use to prepare the solution.

......

...... (6) (Total 14 marks)

Q2.The maximum errors for the pipette and the burette are shown below. These errors take into account multiple measurements.

Page 2 Pipette ± 0.05 cm3 Burette ± 0.15 cm3

Estimate the maximum percentage error in using each of these pieces of apparatus.

Use an average titre 24.25 cm3 to calculate the percentage error in using the burette.

Show your working.

Pipette ......

......

Burette ......

...... (Total 2 marks)

Q3.A teacher noticed that a student had not cleared a large air bubble from below the burette tap in preparing the burette for use before starting the titration. This air bubble was ejected during the first titration of the volumetric flask mixture.

(a) State the effect that this mistake would have on the value of the first titre.

......

...... (1)

(b) State and explain the effect, if any, that this mistake would have on the average titre for this experiment.

......

...... (2) (Total 3 marks)

Q4.The correct technique can improve the accuracy of a titration. Page 3 (a) State why it is important to fill the space below the tap in the burette with solution A before beginning an accurate titration.

......

...... (1)

(b) Suggest one reason why a 250 cm3 conical flask is preferred to a 250 cm3 beaker for a titration.

......

...... (1)

(c) During a titration, a chemist rinsed the inside of the conical flask with deionised water. The water used for rinsing remained in the conical flask.

(i) Give one reason why this rinsing can improve the accuracy of the end-point.

......

...... (1)

(ii) Explain why the water used for rinsing has no effect on the accuracy of the titre.

......

...... (1)

(d) Suggest one reason why repeating a titration makes the value of the average titre more reliable.

......

...... (1) (Total 5 marks)

Page 4 Q5.This question concerns the oxidation of a primary alcohol.

The experiment was carried out using the distillation apparatus shown in the diagram. The oxidation product was distilled off as soon as it was formed.

(a) Suggest the identity of reagent P.

...... (1)

(b) State the chemical change that causes the solution in the flask to appear green at the end of the reaction.

...... (1)

......

...... (1)

Page 5 (d) Suggest a reagent that could be used to confirm the presence of an aldehyde in the distillate. State the observation you would expect to make if an aldehyde were present.

Reagent ......

Observation ...... (2) (Total 5 marks)

Q6.An experiment was carried out to determine the equilibrium constant, Kc, for the following reaction.

CH3CH2COOH + CH3CH2CH2OH CH3CH2COOCH2CH2CH3 + H2O

A student added measured volumes of propan-1-ol and propanoic acid to a conical flask. A measured volume of concentrated hydrochloric acid was added to the flask, which was then sealed.

After 1 week, the contents of the flask were poured into water and the solution was made up to a known volume. This solution was titrated with standard sodium hydroxide solution.

(a) Explain how the student could determine the amount, in moles, of propan-1-ol added to the flask.

......

...... (2)

(b) The titration described above gives the total amount of acid in the equilibrium mixture. Explain how, by carrying out a further experiment, the student could determine the amount of propanoic acid in the equilibrium mixture.

......

...... (2)

Page 6 (c) In a repeat experiment, the student failed to seal the flask that contained the equilibrium mixture.

Explain why this error would lead to the student obtaining an incorrect value for the equilibrium constant Kc

......

...... (2) (Total 6 marks)

Q7.(a) Write an equation for the reaction that occurs when magnesium is heated in steam. Describe what you would observe when this reaction occurs.

Equation ......

Observations ......

......

...... (3)

(b) Write an equation for the reaction that occurs when sodium is heated in oxygen. Describe what you would observe when this reaction occurs.

Equation ......

Observations ......

......

...... (3) (Total 6 marks)

Q8.Alcohols such as methanol (CH3OH), ethanol (CH3CH2OH) and propan-1-ol (CH3CH2CH2OH) are good fuels.

Page 7 (a) A student carried out an experiment to determine the enthalpy of combustion of methanol.

Methanol was placed in a spirit burner and the mass of the spirit burner measured. The student placed 100 g of water in a copper calorimeter and clamped it above the spirit burner. The burner was lit and allowed to burn for a few minutes. The flame was then extinguished and the new mass of the spirit burner found.

The measured temperature rise was 38.0 °C. The specific heat capacity of water is 4.18 J K−1 g−1.

A diagram of the apparatus is shown alongside a table which shows the measurements the student recorded.

Use the student’s data to calculate an experimental value for the enthalpy of combustion of methanol in kJ mol−1.

......

...... (4)

(b) Suggest one reason, other than incomplete combustion or heat transfer to the atmosphere, why the student’s value for the enthalpy of combustion of methanol is different from that in a Data Book.

Page 8 ......

...... (1)

(c) The uncertainty in each of the temperature readings from the thermometer in this experiment was ±0.25 °C. This gave an overall uncertainty in the temperature rise of ±0.5 °C.

Calculate the percentage uncertainty for the use of the thermometer in this experiment.

......

...... (1)

(d) The student said correctly that using a thermometer with an overall uncertainty for the rise in temperature of ±0.5 °C was adequate for this experiment.

Explain why this thermometer was adequate for this experiment.

......

...... (1)

(e) The enthalpy of combustion of ethanol is −1371 kJ mol−1. The density of ethanol is 0.789 g cm−3.

Calculate the heat energy released in kJ when 0.500 dm3 of ethanol is burned. Give your answer to an appropriate number of significant figures.

......

...... (3) (Total 10 marks)

Q9.Calamine lotion can contain a mixture of zinc carbonate and zinc oxide in suspension in water. A manufacturer of calamine lotion claims that a sample contains 15.00 g of zinc carbonate and 5.00 g of zinc oxide made up to 100 cm3 with distilled water. Page 9 (a) A chemist wanted to check the manufacturer’s claim. The chemist took a 20.0 cm3 sample of the calamine lotion and added it to an excess of sulfuric acid. The volume of carbon dioxide evolved was measured over time. The chemist’s results are shown in the table.

Time / s 0 15 30 45 60 75 90 105 120 135

Volume / cm3 0 135 270 380 470 530 560 570 570 570

(i) Plot a graph of the results in the table on the grid. The volume should be on the y-axis. Draw a best-fit curve through all the points. (3)

(ii) Estimate the time taken for the reaction to be completed.

...... (1)

Page 10

(b) (i) The volume of carbon dioxide in part (a) was measured at 293 K and at a

Page 11 pressure of 100 kPa.

Use information from your graph to calculate the maximum amount, in moles, of carbon dioxide evolved from the zinc carbonate in this 20.0 cm3 sample.

The gas constant, R = 8.31 J K−1 mol−1

Show your working.

......

...... (3)

(ii) Use your answer to part (i) to calculate the mass of zinc carbonate in the 20.0 cm3 sample of calamine lotion.

(If you were unable to complete part (i), you may assume that the amount of carbon dioxide evolved was 0.0225 mol. This is not the correct answer.)

......

...... (2)

(iii) Calculate the difference between your answer to part (ii) and the manufacturer’s claim that there are 15.00 g of zinc carbonate in 100 cm3 of the calamine lotion.

Express this difference as a percentage of the manufacturer’s claim.

(If you were unable to complete part (ii), you may assume that the mass of zinc carbonate in the 20 cm3 sample of calamine lotion was 2.87 g. This is not the correct answer.)

Difference ......

Percentage ......

......

Page 12 (2)

(c) Draw a diagram of a suitable apparatus needed to perform the experiment outlined in part (a). Include in your diagram a method for collecting and measuring the carbon dioxide. The apparatus should be airtight. (2) (Total 13 marks)

Q10.A value for the enthalpy of combustion of an alcohol can be determined using the apparatus shown in the diagram. The calorimeter is held in position by a clamp.

This experiment can be repeated by using a different volume of water that would result in a more accurate value for the enthalpy of combustion because there would be a reduction in the heat lost.

State a change in the volume of water that would cause a reduction in heat loss and explain your answer.

Change in volume: ......

Explanation: ......

...... (Total 2 marks)

Q11.When boric acid (H3BO3) is applied as a coating on wood, it acts as a fire retardant by decreasing the rate of combustion.

Page 13 Thermal decomposition of boric acid takes place in two stages.

In an experiment a sample of boric acid was heated in a crucible at 170 °C. The results of this experiment are given in the table.

Time of heating / minutes Mass of crucible and contents / g

0 35.85

5 35.10

10 34.41

15 34.00

20 33.70

25 33.56

30 33.50

35 33.50

Plot a graph of the results from the table above to show the mass of the crucible and boric acid (y-axis) against time of heating on the grid.

Page 14

(Total 4 marks)

Page 15

Q12.A laboratory technician discovered four badly−labelled bottles, each containing one pure white solid. Each bottle contained a compound of a different Group 2 metal (magnesium, calcium, strontium and barium).

Some tests were carried out on the solids or, if the compound was soluble, on the aqueous solution. The results are given in the table.

Test Compound 1 Compound 2 Compound 3 Compound 4

Added to Dissolves Insoluble Dissolves Dissolves water

Gives off Solution Solution or Solution carbon dioxide Solution remains solid added to remains gas and a remains colourless and HCl(aq) colourless colourless colourless heat released solution forms

Solution or Solution gives Solution gives Solution has Solid remains solid added to a white a slight white no visible insoluble NaOH(aq) precipitate precipitate change

Gives off Solution Solution or Solution has carbon dioxide Solution forms slowly forms a solid added to no visible gas and a a white slight white H2SO4(aq) change white solid precipitate precipitate remains

(a) One of the bottles has a very faint label that could be read as ‘Magnesium Sulfate’.

Use the information in the table to deduce which one of the four compounds is magnesium sulfate and explain your answer.

Compound ......

Explanation ......

......

...... (3)

(b) The bottle containing Compound 2 has a ‘TOXIC’ hazard symbol.

Use the information in the table to identify Compound 2.

Page 16 Explain both observations in the reaction with H2SO4(aq).

Identity of Compound 2 ......

Explanation ......

......

...... (3)

Give an equation for the reaction of strontium hydroxide with sulfuric acid.

Compound ......

......

Equation ......

...... (2) (Total 8 marks)

Q13.Propane-1,2-diol has the structure CH2(OH)CH(OH)CH3. It is used to make polyesters and is one of the main substances in electronic cigarettes (E-cigarettes).

A sample of propane-1,2-diol was refluxed with a large excess of potassium dichromate(VI) and sulfuric acid.

(a) Draw the skeletal formula of propane-1,2-diol.

(1)

(b) Write an equation for this oxidation reaction of propane-1,2-diol under reflux, using [O] to represent the oxidizing agent.

Show the displayed formula of the organic product.

Page 17 ...... (2)

(2)

(d) Anti-bumping granules are placed in the flask when refluxing. Suggest why these granules prevent bumping.

......

...... (1)

(e) Draw the structure of a different organic product formed when the acidified potassium dichromate(VI) is not in excess.

(1) (Total 7 marks)

Q14.(a) Suggest one reason why sugars are often added to antacid tablets.

......

Page 18 ......

...... (1)

(b) In one titration, a student added significantly more phenolphthalein than instructed. The volume of sodium hydroxide solution in this titration was greater than the average value of the concordant titres.

State a property of the indicator that would explain this result.

......

...... (1)

Suggest why this may be a disadvantage when used as a medicine to relieve indigestion.

......

...... (1) (Total 3 marks)

Q15.A student carried out an experiment to determine the number of C=C double bonds in a molecule of a cooking oil by measuring the volume of bromine water decolourised.

The student followed these instructions:

• Use a dropping pipette to add 5 drops of oil to 5.0 cm3 of inert organic solvent in a conical flask. • Use a funnel to fill a burette with bromine water. • Add bromine water from a burette to the solution in the conical flask and swirl the flask after each addition to measure the volume of bromine water that is decolourised.

The student’s results are shown in the table below.

Experiment Volume of bromine water / cm3

1 39.40

Page 19 2 43.50

3 41.20

(a) In a trial experiment, the student failed to fill the burette correctly so that the gap between the tap and the tip of the burette still contained air.

Suggest what effect this would have on the measured volume of bromine water in this trial. Explain your answer.

......

...... (2)

(b) Other than incorrect use of the burette, suggest a reason for the inconsistency in the student’s results.

...... (1)

(c) Outline how the student could improve this practical procedure to determine the number of C=C double bonds in a molecule of the oil so that more consistent results are obtained.

......

...... (4)

Page 20 (d) The oil has a density of 0.92 g cm–3 and each of the 5 drops of oil has a volume of 5.0 × 10–2 cm3.

The approximate Mr of the oil is 885. The concentration of bromine water used was 2.0 × 10–2 mol dm–3.

Use these data and the results from experiment 1 to deduce the number of C=C double bonds in a molecule of the oil. Show your working.

(5) (Total 12 marks)

Q16.Barium chloride solution was added, dropwise, to magnesium sulfate solution until no more white precipitate was formed. The mixture was filtered.

Give the formulae of the two main ions in the filtrate.

......

...... (Total 1 mark)

Q17.A desiccator can be used to dry precipitates as shown in the diagram.

Page 21

(a) Explain briefly how the precipitate in the desiccator becomes dry.

......

...... (1)

(b) Anhydrous cobalt(II) chloride is blue. It is often added to the drying agent to indicate the amount of moisture in the drying agent.

State the colour change of this cobalt compound that you would observe as the drying process takes place.

...... (1) (Total 2 marks)

Q18.The following pairs of compounds can be distinguished by simple test−tube reactions.

For each pair of compounds, give a reagent (or combination of reagents) that, when added separately to each compound, could be used to distinguish between them. State what is observed in each case.

(a) Butan−2−ol and 2−methylpropan−2−ol

Reagent ......

Observation with butan−2−ol

......

Observation with 2−methylpropan−2−ol

......

Page 22 ...... (3)

(b) Propane and propene

Reagent ......

Observation with propane

......

Observation with propene

......

...... (3)

Reagent ......

Observation with aqueous silver nitrate

......

Observation with aqueous sodium nitrate

......

...... (3)

(d) Aqueous magnesium chloride and aqueous barium chloride

Reagent ......

Observation with aqueous magnesium chloride

......

Observation with aqueous barium chloride

......

Page 23 ...... (3) (Total 12 marks)

Q19.In a titration, it is important to wash the inside of the titration flask with distilled or deionised water as you approach the end-point.

(a) Suggest one reason why it is important to wash the inside of the flask.

......

...... (1)

(b) Washing with water decreases the concentration of the reagents in the titration flask.

Suggest why washing with water does not affect the titre value.

......

...... (1) (Total 2 marks)

Q20.This question is about the chemical properties of chlorine, sodium chloride and sodium bromide.

(a) Sodium bromide reacts with concentrated sulfuric acid in a different way from sodium chloride.

Write an equation for this reaction of sodium bromide and explain why bromide ions react differently from chloride ions.

Equation ......

Explanation ......

......

...... (3)

Page 24

(b) A colourless solution contains a mixture of sodium chloride and sodium bromide.

......

...... (6)

(c) Write an ionic equation for the reaction between chlorine and cold dilute sodium hydroxide solution. Give the oxidation state of chlorine in each of the chlorine-containing ions formed.

......

...... (2) (Total 11 marks)

Q21.This question is about reactions of calcium compounds.

(a) A pure solid is thought to be calcium hydroxide. The solid can be identified from its relative formula mass.

The relative formula mass can be determined experimentally by reacting a measured mass of the pure solid with an excess of hydrochloric acid. The equation for this

Page 25 reaction is

Ca(OH)2 + 2HCl CaCl2 + 2H2O

The unreacted acid can then be determined by titration with a standard sodium hydroxide solution.

You are provided with 50.0 cm3 of 0.200 mol dm−3 hydrochloric acid. Outline, giving brief practical details, how you would conduct an experiment to calculate accurately the relative formula mass of the solid using this method.

......

...... (8)

(b) A 3.56 g sample of calcium chloride was dissolved in water and reacted with an excess of sulfuric acid to form a precipitate of calcium sulfate.

The percentage yield of calcium sulfate was 83.4%.

Calculate the mass of calcium sulfate formed. Give your answer to an appropriate number of significant figures.

Mass of calcium sulfate formed = ...... g (3) (Total 11 marks)

Page 26 Q22.(a) Strontium chloride is used in toothpaste for sensitive teeth. Both strontium carbonate and strontium sulfate are white solids that are insoluble in water.

(i) Write an equation for the reaction between strontium chloride solution and sodium sulfate solution. Include state symbols in your equation.

...... (1)

(ii) Strontium carbonate reacts with nitric acid to produce a solution of strontium nitrate. Strontium sulfate does not react with nitric acid.

Describe briefly how you could obtain strontium sulfate from a mixture of strontium carbonate and strontium sulfate. You are not required to describe the purification of the strontium sulfate.

......

...... (2)

(b) A solution of magnesium sulfate is sometimes given as first aid to someone who has swallowed barium chloride.

Explain why drinking magnesium sulfate solution is effective in the treatment of barium poisoning.

......

...... (1)

Describe briefly how you would carry out this test and state what you would observe.

......

Page 27 ......

......

...... (3) (Total 7 marks)

Page 28 Mark scheme

M1.(a) Selects correct titres If 3 or more titres used them MAX 1 for conseq M3 1

= 9.7(0) cm3 Calculates mean 1

mol HCL = 0.102 × 9.70/1000 = 9.89 × 10−4(allow 9.9 × 10-4 for M3 but check not via 4 titres in which case only 1 mark) Calculates mol (working or result gains credit) 9.92 × 10−4 scores 1 if all 4 titres used 9.83 × 10−4 scores 1 if titres 1,2, and 3 used 1

−3 (b) mol MHCO3 = ANS 3.1 × 10 (= 9.89 × 10 ) Use ecf if wrong mean calculated above 1

Mr = 148 (3sf) Allow ecf following wrong mass conversion 1

(c) Suggestion: Use a larger mass of solid OR use a more concentrated solution of MHCO3 OR less concentrated / more dilute solution of HCl OR more MHCO3 1 Cannot score justification mark unless suggestion correct, but suggestion could be after justification

Justification: So a larger titre/reading will be needed OR larger volume of HCl

Assume reference to the solution means the MHCO3 1

(d) This question is marked using levels of response.

Level 3 Must use volumetric flask to access level 3 Answer is communicated coherently and shows a logical

Page 29 progression from stage 1 to stage 2 then stage 3.

All stages are covered and the description of each stage is complete 6 marks All stages are covered but up to 2 omissions/errors from different stages. If 2 omissions/errors from same stage only level 2 possible 5 marks

Level 2 Answer is mainly coherent and shows progression from stage 1 to stage 3

All stages are covered but 3 omissions/errors 4 marks All stages are attempted 3 marks

Level 1 Answer includes isolated statements but these are not presented in a logical order or show confused reasoning.

2 stages attempted 2 marks 1 stage attempted 1 mark

Level 0 Insufficient correct chemistry to gain a mark. 0 marks

Indicative Chemistry content Stage 1: transfers known mass of solid a) Weigh the sample bottle containing the solid on a (2 dp) balance b) Transfer to beaker* and reweigh sample bottle c) Record the difference in mass Or d) Place beaker* on balance and tare e) Transfer solid into beaker f) Record mass Or g) Known mass provided h) Transfers (known) mass into beaker* i) Wash all remaining solid from sample bottle into beaker Allow use of weighing boat *Allow other suitable glassware including volumetric flask

Page 30

Stage 2: Dissolves in water a) Add distilled / deionised water b) Stir (with a glass rod) or swirl c) Until all solid has dissolved

Stage 3: Transfer, washing and agitation a) Transfer to volumetric / graduated flask. Allow if a clear description/diagram given eg long necked flask with 250 cm3 mark b) With washings c) Make up to 250 cm3 / mark with water d) Shakes/inverts/mixes 6 [14]

M2.Pipette = 0.05 × 100 / 25.0 = 0.2% Ignore precision 1

Burette = 0.15 × 100 / 24.25 cm3 Must show working Allow one mark for two correct answers with no working 1 [2]

M3.(a) The value of the titre would be higher (than the true value.) 1

(b) It should have no effect. 1

The first titration can be ignored / subsequent titrations would be accurate Allow references to the first titration being a ‘rough’ or ‘trial’ value. 1 [3]

M4.(a) Space will fill during titration / titres or volumes added are too high

Page 31 Do not allow ‘to improve accuracy’ without qualification. Do not allow ‘incorrect end-point’ without qualification. Do not allow ‘titres or volumes added are too low’. Ignore ‘titres or volumes added are different’. 1

(b) Less chance of losing liquid on swirling / liquid doesn’t splash on swirling Do not accept ‘easier to swirl’ on its own. 1

(c) (i) Returns reagent on the sides of the flask to the reaction mixture (to ensure that all of the acid / alkali reacts) Do not allow ‘to improve accuracy’ without qualification. Ignore reference to cleaning. 1

(ii) This does not change the number of moles of reagents / water is not a reagent / water is one of the products Do not allow ‘water does not affect the titration’ without qualification. Ignore ‘water is neutral / has a pH of 7’. 1

(d) Idea that a single titration could be flawed / anomalous Do not accept ‘will improve reliability / reproducibility / accuracy’ without further qualification. Allow ‘to obtain concordant results’. 1 [5]

M5.(a) H2SO4

Allow H3PO4 or HCl 1

(b) Dichromate / Cr(VI) reduced or Cr(III) formed. Allow Cr6+ and Cr3+ 1

Page 32 (c) The alcohol is flammable Allow enables temperature to be controlled 1

(d) Tollens’ 1

Silver mirror OR Fehling’s Red precipitate OR Benedict’s Red precipitate 1 [5]

M6.(a) Multiply volume of propan−1−ol by density Allow measure the mass of the volume added Any reference to concentration of propan−1−ol CE = 0 1

Divide the mass by the Mr of propan−1−ol 1

(b) Titrate a measured volume of the concentrated HCl added initially to determine moles of HCl used in the experiment

Allow addition of AgNO3 to form AgCl precipitate. Use mass of precipitate to calculate initial moles of HCl added. 1

Subtract this number of moles of HCl from the total moles of acid at equilibrium 1

M2 incorrect values used (to determine Kc) Allow the system will no longer be at equilibrium Do not allow references to equilibrium position shifting alone 1 [6]

Page 33

M7.(a) Mg + H2O → MgO + H2 ignore state symbols 1

White solid / powder / ash / smoke ignore precipitate ignore fumes 1

(Bright) white light / flame allow glow penalise effervescence under list principle 1

(b) 2Na + O2 → Na2O / 4Na + O2 → 2Na2O Allow multiples, ignore state symbols

Allow 2Na + O2 → Na2O2 1

white / yellow solid / ash / smoke ignore precipitate ignore fumes 1

orange / yellow flame 1 [6]

M8.(a) M1 (q = mcΔT = 100 × 4.18 × 38(.0)) = 15 884 / 15 880 / 15 900 / 16 000 (J) (OR 15.884 / 15.88 / 15.9 / 16 (kJ)) Award full marks for correct answer Mark is for value not expression (at least 2sf); penalise incorrect units here only if M1 is the only potential scoring point in M1-M3 1

M2 Moles (methanol = 1.65 / 32.0) = 0.0516 or 0.052 At least 2sf 1

M3 Heat change per moles = M1/M2 (15 884 / 0.0516 / 1000 = 308 (kJ mol−1) (allow 305 to 310) At least 2sf; answer must be in kJ mol−1

Page 34 1

M4 Answer = −308 (kJ mol−1) (allow −305 to −310) This mark is for – sign (mark independently) 1

(b) Heating up copper / calorimeter / container / thermometer / heat capacity of copper / calorimeter / thermometer not taken into account OR Evaporation of alcohol/methanol OR Experiment not done under standard conditions Not human errors (e.g. misreading scales) Not impure methanol Allow evaporation of water 1

(d) Idea that heat loss is more significant issue OR Idea that temperature change/rise is (significantly / much) bigger than uncertainty One of these two ideas only and each one must involve a comparison 1

(e) M1 Mass of ethanol = 500 × 0.789 (= 394.5 or 395 (g)) 1

M2 Moles of ethanol = M1 / 46.0 (= 8.576 or 8.58) 1

M3 Heat released = M2 × 1371 = 11800 (kJ) must be 3 sf 1 Correct answer to 3sf scores 3; correct value to 2sf or more than 3sf scores 2 Answers that are a factor of 10x out score 2 if given to 3sf or 1 if given to a different number of sf M3 ignore units, but penalise incorrect units M3 ignore sign M2 and M3 – allow consequential marking [10]

Page 35 M9.(a) (i) Uses sensible scales. Lose this mark if the plotted points do not cover half of the paper. Lose this mark if the graph plot goes off the squared paper Lose this mark if volume is plotted on the x-axis 1

All points plotted correctly Allow ± one small square. 1

(ii) Any value in the range 91 to 105 s Allow a range of times within this but not if 90 quoted. 1

(b) (i) Using pV = nRT This mark can be gained in a correctly substituted equation. 1

100 000 × 570 × 10−6 = n × 8.31 × 293 Correct answer with no working scores one mark only. 1

n = 0.0234 mol Do not penalise precision of answer but must have a minimum of 2 significant figures. 1

(ii) Mol of ZnCO3 = 0.0234 Mark consequentially on Q6

M1 1

Mass of ZnCO3 = M1 × 125.4 = 2.9(3) or 2.9(4) g If 0.0225 used then mass = 2.8(2) g

M2 1

(iii) Difference = (15.00 / 5) − Ans to b If 2.87 g used then percentage is 4.3

M1 1

Percentage = (M1 / 3.00) × 100 Ignore precision beyond 2 significant figures in the final

Page 36 answer If 2.82 g used from (ii) then percentage = 6.0

M2 1

Gas collection over water or in a syringe Collection vessel must be graduated by label or markings Ignore any numbered volume markings. 1 [13]

M10.Increase in volume If a volume is quoted it must be less than 300 1

Smaller increase in T above room temperature Or increased contact between calorimeter and water Or smaller heat loss by evaporation / from the surface 1 [2]

M11.Mass of crucible and boric acid on the y−axis Axes must be labelled but do not penalise lack of units (unless incorrect). 1

Suitable scale used Plotted points must cover at least half the printed grid.(both directions). 1

All points plotted correctly Allow + / − one small square. 1

Page 37 Suitable line drawn Good best−fit line based on their points (+ / − one small square). Do not award if kinked, doubled or very thick line. 1 [4]

M12.(a) Compound 1 If M1 incorrect, CE = 0

M1 1

No visible change with H2SO4

M2 1

Gives white ppt with NaOH

M3 1

(b) BaCO3 1

The carbonate ion releases CO2 1

but the BaSO4 formed is highly insoluble. 1

Sr(OH)2 + H2SO4 SrSO4 + 2H2O Allow ionic equation; ignore state symbols 1 [8]

M13.(a) Any correct skeletal formula (both OH groups must be shown)

Page 38 1

(b) M1 Displayed formula of correct product Incorrect organic product CE=0 Must be displayed formula but can be shown separately or in the equation 1

M2 Balanced equation

Allow any correct structural formula (or molecular formula C3H4O3) for product in balanced equation Allow any correct formula of propane-1,2-diol (including its molecular formula C3H8O2) 1

(c) M1 flask with condenser vertically above it (without gaps between flask and condenser) Distillation diagram CE = 0 Condenser must have outer tube for water that is sealed at top and bottom; condenser must have two openings for water in/out (that are open, although these openings do not need to be labelled) Penalise M1 if apparatus is sealed (a continuous line across the top and/or bottom of the condenser is penalised) 1

M2 flask and condenser labelled Allow condensing tube for condenser label 1

(d) Form small(er) bubbles or prevent large bubbles 1

Page 39 (e) Any one of these four structures:

Allow any correct structural / displayed / skeletal formula For reference:

Carbon 1 Carbon 2 aldehyde alcohol carboxylic acid alcohol aldehyde ketone alcohol ketone

1 [7]

M14.(a) (To make chewing the tablets) more palatable

Tastes better / sweet taste / mask the taste of the Mg(OH)2 Do not allow ‘to aid digestion’. 1

(b) The indicator is acidic 1

M15.(a) Measured volume would be greater 1

Level in burette falls as tap is filled before any liquid is delivered 1

(b) Drop sizes vary Allow percentage error for amount of oil will be large as the amount used is so small 1

Page 40 (c) Use a larger single volume of oil 1

Dissolve this oil in the organic solvent 1

Transfer to a conical flask and make up to 250 cm3 with more solvent 1

Titrate (25 cm3) samples from the flask 1

(d) Stage 1

Mass of oil = 0.92 × (5.0 × 10–2 × 5) = 0.23 (g) 1

Mol of oil = 0.23 / 885 = 2.6 × 10–4 1 Extended response calculation To gain 4 or 5 marks, students must show a logical progression from stage 1 and stage 2 (in either order) to stage 3

Stage 2

Mol bromine = 2.0 × 10–2 × 39.4 / 1000 = 7.9 × 10–4 1

Stage 3

Ratio oil : bromine

2.6 × 10–4 : 7.9 × 10–4

Simplest ratio = 2.6 × 10–4 / 2.6 × 10-4 : 7.9 × 10–4 / 2.6 × 10–4

= 1 : 3 1

Page 41

Hence, 3 C=C bonds M5 cannot be awarded unless working for M4 is shown 1 [12]

M16.Mg2+ and Cl– Do not allow names. [1]

M17.(a) Water in the gaseous state from the precipitate absorbed by drying agent

Water vapour from the precipitate absorbed by drying agent Allow ‘water vapour reacts with drying agent’. Do not allow ‘absorb water’ without qualification. 1

(b) (Blue to) pink / pink colour observed 1 [2]

M18.(a) M1 acidified potassium dichromate or K2Cr2O7 / H2SO4

+ OR K2Cr2O7 / H OR acidified K2Cr2O7

M2 (orange to) green solution OR goes green

Alternative using KMnO4 / H2SO4

Page 42 M1 acidified potassium manganate(VII) / potassium permanganate or KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 colourless solution OR goes colourless

Credit alkaline KMnO4 for possible full marks but M2 gives brown precipitate or solution goes green 3

(b) M1 (Shake with) Br2 OR bromine (water) OR bromine (in CCl4 / organic solvent)

M2 (stays) orange / red / yellow / brown / the same

OR no reaction OR no (observed) change

OR as alternatives

Use KMnO4 / H2SO4

M1 acidified potassium manganate(VII) / potassium permanganate OR KMnO4 / H2SO4

+ OR KMnO4 / H OR acidified KMnO4

M2 (stays) purple or no reaction or no (observed) change

M3 decolourised / goes colourless / loses its colour

Use iodine

M1 iodine or I2 / KI or iodine solution

M2 no change

Page 43 M3 decolourised / goes colourless / loses its colour

Use concentrated sulfuric acid

M1 concentrated H2SO4

M2 no change

M2 white precipitate or white solid / white suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble iodide including HI

M2 yellow precipitate or yellow solid / yellow suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 Any soluble bromide including HBr

M2 cream precipitate or cream solid / cream suspension

M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

OR as an alternative

M1 NaOH or KOH or any soluble carbonate

M2 brown precipitate or brown solid / brown suspension with NaOH / KOH (white precipitate / solid / suspension with carbonate)

Page 44 M3 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear If no reagent or incorrect reagent or insoluble chloride in M1, CE = 0 and no marks for M1, M2 or M3 Allow chlorine water If incomplete reagent (e.g. chloride ions) or inaccurate attempt at formula of chosen chloride, or chlorine, penalise M1 only and mark on For M2 require the word “white” and some reference to a solid. Ignore “cloudy solution” OR “suspension” (similarly for the alternatives) For M3 Ignore “nothing (happens)” Ignore “no observation” Ignore “clear” on its own Ignore “dissolves” 3

(d) M1 Any soluble sulfate including (dilute or aqueous) sulfuric acid

M2 remains colourless or no reaction or no (observed) change or no precipitate or clear solution or it remains clear

M3 white precipitate or white solid / white suspension If no reagent or incorrect reagent or insoluble sulfate in M1, CE = 0 and no marks for M1, M2 or M3

OR as an alternative

M1 NaOH or KOH

M2 white precipitate or white solid / white suspension

Page 45 and mark on

If M1 uses NH3 (dilute or concentrated) penalise M1 only and mark on 3 [12]

M19.(a) To make sure all the solutions (from both the burette and pipette) react with each other / are in the flask Penalise ‘solid’ or ‘residue’. Do not allow any suggestion of removal of species. 1

(b) Water does not change the number of moles of either reagent / reactants Water is not a reagent / does not react with either reactant. Do not allow ‘water is not involved in the reaction’. Apply list principle. 1 [2]

M20.(a) 2NaBr + 2H2SO4 Na2SO4 + Br2 + SO2 + 2H2O Allow ionic equation

– 2– 2Br + 2H2SO4 Br2 + SO4 + SO2 + 2H2O 1

Br– ions are bigger than Cl– ions 1

Therefore Br– ions more easily oxidised / lose an electron more easily (than Cl– ions) 1

(b) This question is marked using levels of response. Refer to the Mark Scheme Instructions for Examiners for guidance on how to mark this question.

Level 3

All stages are covered and the explanation of each stage is generally correct and virtually complete. Stages 1 and 2 are supported by correct equations.

Page 46 Answer communicates the whole process coherently and shows a logical progression from stage 1 to stage 2 and then stage 3. The steps in stage 3 are in a logical order. 5–6 marks

Level 2

All stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies OR two stages are covered and the explanations are generally correct and virtually complete.

Answer is mainly coherent and shows a progression through the stages. Some steps in each stage may be out of order and incomplete. 3–4 marks

Level 1

Two stages are covered but the explanation of each stage may be incomplete or may contain inaccuracies, OR only one stage is covered but the explanation is generally correct and virtually complete.

Answer includes some isolated statements, but these are not presented in a logical order or show confused reasoning. 1–2 marks

Level 0

Insufficient correct chemistry to warrant a mark. 0 marks Indicative chemistry content Stage 1: formation of precipitates • Add silver nitrate • to form precipitates of AgCl and AgBr

• AgNO3 + NaCl → AgCl + NaNO3

• AgNO3 + NaBr → AgBr + NaNO3

Stage 2: selective dissolving of AgCl • Add excess of dilute ammonia to the mixture of precipitates • the silver chloride precipitate dissolves + − • AgCl + 2NH3 → Ag(NH3)2 + Cl

Stage 3: separation and purification of AgBr • Filter off the remaining silver bromide precipitate • Wash to remove soluble compounds • Dry to remove water 6

Page 47

– – – (c) Cl2 + 2HO OCl + Cl + H2O 1

OCl– is +1

Cl– is –1 Both required for the mark 1 [11]

M21.(a) Stage 1: appreciation that the acid must be in excess and calculation of amount of solid that permits this

Statement that there must be an excess of acid 1

Moles of acid = 50.0 × 0.200 / 1000 = 1.00 × 10–2 mol 1

2 mol of acid react with 1 mol of calcium hydroxide therefore moles of solid weighed out must be less than half the moles of acid = 0.5 × 1.00 × 10–2 = 5.00 × 10–3 mol 1

Mass of solid must be –3 × 74.1 = 1

Stage 2: Experimental method

Measure out 50 cm3 of acid using a pipette and add the weighed amount of solid in a conical flask 1

Titrate against 0.100 (or 0.200) mol dm–3 NaOH added from a burette and record the volume (v) when an added indicator changes colour 1

Page 48

Stage 3: How to calculate Mr from the experimental data

Moles of calcium hydroxide = 5.00 × 10–3 – (v/2 × conc NaOH) / 1000 = z mol 1

Mr = mass of solid / z 1 Extended response Maximum of 7 marks for answers which do not show a sustained line of reasoning which is coherent, relevant, substantiated and logically structured.

(b) Moles of calcium chloride = 3.56 / 111.1 = 3.204 × 10–2 1

Moles of calcium sulfate = 3.204 × 10–2 × 83.4 / 100 = 2.672 × 10–2 1

Mass of calcium sulfate = 2.672 × 10–2 × 136.2 = 3.6398 = 3.64 (g) Answer must be to 3 significant figures 1 [11]

M22.(a) (i) SrCl2(aq) + Na2SO4(aq) → SrSO4(s) + 2NaCl(aq) Allow multiples, including fractions. Allow ionic equations. Lose this mark if any of the state symbols are missing or incorrect. 1

(ii) Add nitric acid to the mixture (until in excess) Do not allow any suggestion that the solution is an emetic. 1

Page 49 Filter (to isolate strontium sulfate) 1

(b) Insoluble barium sulfate is formed Allow ‘removes barium ions as a precipitate’. 1

Cream precipitate M2 Allow ‘off white precipitate’. 1

Page 50