C8 Identification of Ions by Chemical and Spectroscopic Means Chem Only

C8 IDENTIFICATION OF IONS BY Name: ______CHEMICAL AND SPECTROSCOPIC MEANS Class: ______Question Practice Date: ______

Time: 164 minutes

Marks: 163 marks

Comments: GCSE CHEMISTRY ONLY

Immanuel+College Page 1 of 60 This question is about reactions of ethanoic acid and the analysis of salts. 1 (a) Figure 1 shows the apparatus used to investigate the reaction of ethanoic acid with calcium carbonate.

(i) Describe a change that would be seen in each test tube.

Give a reason for each change.

Test tube 1 ______

______

Test tube 2 ______

______

______(4)

(ii) Complete the displayed structure of ethanoic acid.

(1)

Immanuel+College Page 2 of 60 (iii) Ethanoic acid is a carboxylic acid. Complete the sentence.

Carboxylic acids react with alcohols in the presence of an

______

catalyst to produce pleasant-smelling compounds

called ______. (2)

(b) Figure 2 shows four test tubes containing three different salt solutions and water.

Each solution and the water was tested with:

• silver nitrate in the presence of dilute nitric acid

• barium chloride in the presence of dilute hydrochloric acid.

Complete the table of results.

Calcium Potassium Ammonium nitrate Water chloride solution sulfate solution solution

Test with silver nitrate in the no change no change presence of dilute nitric acid

Test with barium chloride in the no change white precipitate presence of dilute hydrochloric acid

(2)

Immanuel+College Page 3 of 60 (c) Flame tests can be used to identify metal ions.

(i) Complete the following sentences.

The flame colour for potassium ions is ______.

The flame colour for calcium ions is ______. (2)

(ii) Give one reason why a flame test would not show the presence of both potassium ions and calcium ions in a mixture.

______

______(1) (Total 12 marks)

Cheshunt mixture is a powder containing copper sulfate, CuSO , and ammonium carbonate, 2 4 (NH4)2CO3

(a) A student tested the Cheshunt mixture.

(i) Hydrochloric acid was added. A gas was produced that turned limewater milky.

Complete the sentence.

The gas was ______which shows

that ______ions are in the mixture. (2)

(ii) Sodium hydroxide solution was added. A gas was produced that indicates that ammonium ions are in the mixture.

Complete the sentence.

The gas was ______which turns

damp red ______blue. (2)

Immanuel+College Page 4 of 60 (b) Cheshunt mixture is dissolved in water before it is used. When the student dissolved the Cheshunt mixture in water it formed a blue solution.

(i) Suggest how the student knew that copper ions are in this solution.

______

______(1)

(ii) The student tested the Cheshunt solution and the result of the test indicated that sulfate ions are in the solution.

Complete the sentence.

The student added a solution of ______in the presence of

dilute hydrochloric acid and a ______precipitate was produced. (2) (Total 7 marks) 3 Read the information in the box and then answer the questions.

Seidlitz Powder is the name of a medicine.

Seidlitz Powder comes as two powders. One powder is wrapped in white paper and contains tartaric acid (C4H6O6). The other powder is wrapped in blue paper and contains potassium sodium tartrate (KNaC4H4O6) and sodium hydrogencarbonate (NaHCO3).

The contents of the blue paper are completely dissolved in water and then the contents of the white paper are added.

The equation which represents this reaction is:

+ 2NaHCO (aq) Na C H O (aq) + 2H O (l) + 2CO (g) C4H6O6 (aq) 3 2 4 4 6 2 2

(a) Describe and give the result of a test to identify the gas produced in this reaction.

______

______(2)

Immanuel+College Page 5 of 60 (b) One of the chemicals in Seidlitz Powder is potassium sodium tartrate (KNaC4H4O6).

Suggest why it would be difficult to identify both potassium ions and sodium ions in potassium sodium tartrate using a flame test.

______

______(1)

(i) Describe and give the result of a chemical test to show that magnesium sulfate contains sulfate ions.

Test ______

______

Result ______

______(2)

(ii) Magnesium sulfate contains magnesium ions.

Describe what you see when sodium hydroxide solution is added to a solution of magnesium sulfate.

______

______(1) (Total 6 marks)

Immanuel+College Page 6 of 60 Read the information about protecting the bottoms of ships. 4 A Copper-bottomed Investment

From the 16th to the 19th century, the bottoms of many wooden ships were protected from marine organisms by being covered with sheets of metal.

At first lead was used on the bottoms of ships, then copper was used until 1832 when Muntz Metal replaced it. Muntz Metal is an alloy of two transition metals, copper and zinc.

Table of data

Lead Copper Muntz Metal

Cost (£/kg) £1.20 £3.20 £2.30

Melting point (°C) 327 1083 904

Stops sea worms attacking wood Yes Yes Yes

Stops barnacles and seaweed No Yes Yes sticking to the bottom of the ship

(a) Use the information to answer the following questions.

(i) Suggest why copper replaced lead.

______

Immanuel+College Page 7 of 60 (1)

(ii) Suggest why Muntz Metal replaced copper.

______

______(1)

(b) A sample of Muntz Metal contains a very small amount of iron as an impurity.

(i) Name an instrumental method of analysis that could be used to detect iron.

______(1)

(ii) Suggest why an instrumental method would detect the iron in this sample of Muntz Metal but a chemical method is not likely to be successful.

______

______(1)

Give two properties of transition metals that make them suitable for making ships.

Property 1 ______

______

Property 2 ______

______(2) (Total 6 marks)

Immanuel+College Page 8 of 60 Alums are salts. They have been used since ancient times in dyeing and medicine and still have 5 many uses today.

Three alums are shown in the table:

Name Ions present

+ 3+ 2- Ammonium alum NH4 Al SO4

+ 3+ 2- Potassium alum K Al SO4

+ 3+ 2- Sodium alum Na Al SO4

2- (a) These alums contain sulfate ions (SO4 ).

Describe and give the result of a chemical test to show this.

Test ______

______

Result ______

______(2)

(b) These alums contain aluminium ions (Al3+).

Describe how sodium hydroxide solution can be used to show this.

______

______(2)

Immanuel+College Page 9 of 60 (c) Aluminium ions do not give a colour in flame tests. However, flame tests can be used to distinguish between these three alums.

Explain how these three alums could be identified from the results of flame tests.

______

______(2) (Total 6 marks)

The label is from a packet of Low Sodium Salt. 6

(a) A student tested some Low Sodium Salt to show that it contains carbonate ions and chloride ions.

(i) Describe and give the result of a test for carbonate ions.

______

______(2)

Immanuel+College Page 10 of 60 (ii) A student identified chloride ions using acidified silver nitrate solution.

State what you would see when acidified silver nitrate solution is added to a solution of Low Sodium Salt.

______(1)

(iii) Flame tests can be used to identify potassium ions and sodium ions.

Suggest why it is difficult to identify both of these ions in Low Sodium Salt using a flame test.

______

______(1)

(b) Read the following information and then answer the questions.

Salt – friend or foe? Sodium chloride (salt) is an essential mineral for our health. It is used to flavour and preserve foods. Too much sodium in our diet may increase the risk of high blood pressure and heart disease. Heart disease is the biggest cause of death in the United Kingdom. Some people claim that excess sodium is a poison that can cause cancer, while others say that more evidence is needed. Many processed foods contain salt, so it is easy to exceed the recommended daily upper limit of about 5 g of salt per person. A ‘healthier’ amount should be about 3 g. In the United Kingdom many people consume over 10 g of salt each day. One way to reduce sodium in our diet is to use Low Sodium Salt. This has two thirds of the sodium chloride replaced by potassium chloride. A national newspaper asked readers for their views on two options. Option 1: Ban the use of sodium chloride in foods. Option 2: Reduce the amount of sodium chloride in all foods to a ‘healthier’ level.

(i) Suggest why Option 1 was rejected.

______

______(1)

Immanuel+College Page 11 of 60 (ii) Suggest two advantages and one disadvantage of Option 2.

______

______(3) (Total 8 marks)

This label has been taken from a packet of My Baby Food. 7 MY BABY FOOD

Infant milk Pure and natural Closest to mothers’ breast milk Contains traces of essential minerals 500 g

One of the minerals in My Baby Food is calcium carbonate, CaCO3.

(a) Chemical tests are used to identify elements and compounds.

(i) A flame test can be used to identify calcium ions. What colour do calcium ions give in a flame test?

______(1)

Immanuel+College Page 12 of 60 (ii) When a flame test was carried out on My Baby Food, the presence of calcium ions was not seen. A yellow flame was produced. Name the ion which gives a yellow flame test.

______(1)

(iii) Suggest one advantage of using an instrumental method to detect the elements present in My Baby Food.

______

______(1)

Immanuel+College Page 13 of 60 (iv) Name an instrumental method for detecting elements.

______(1)

(b) Read the information in the box below and then answer the question.

Calcium carbonate occurs naturally as marble and limestone. They are important building materials and are often used for gravestones. Calcium carbonate is also an essential mineral for good health and is present in many baby foods in small amounts. My Baby Food is recommended as being the closest to a mother’s own breast milk. It is given free to mothers in the developing world – without it their babies might die of malnutrition. Responsible Mothers Are Us (RMAU) is a United Kingdom pressure group. They want to ban chemicals in baby foods. The group was founded by Mrs I. M. Right who has made a career in ‘goodness’ and is paid from donations given to RMAU by members of the public. When interviewed, she said: “Calcium carbonate is a chemical and so it is a pollutant. My Baby Food must be banned to prevent the mass medication of babies. I don’t feed my baby the stuff of gravestones.”

Many people do not agree with Mrs Right’s ideas.

Suggest why.

______

______(3) (Total 7 marks)

Chlorine and bromine are important Group 7 elements. 8 (a) Explain why chlorine is added to drinking water.

______

______(1)

Immanuel+College Page 14 of 60 (b) Describe what you would see when bromine water is added to an unsaturated organic compound.

______

______(1)

(c) Bromine can be extracted from seawater. The dissolved bromide ions are reacted with chlorine. Bromine and chloride ions are formed.

(i) Complete and balance the equation below, which represents the reaction between chlorine and bromide ions.

– Cl2 + 2Br → ______+ ______(1)

(ii) Describe what you see when chlorine is added to a solution containing bromide ions.

______

______(1)

(d) In terms of electronic structure:

(i) state why bromine and chlorine are both in Group 7

______

______(1)

(ii) explain why bromine is less reactive than chlorine.

______

______(3)

Immanuel+College Page 15 of 60 (e) What is the result of adding acidified silver nitrate solution to a solution containing:

(i) chloride ions

______(1)

(ii) bromide ions?

______(1) (Total 10 marks)

Immanuel+College Page 16 of 60 Chemical tests can be used to identify compounds. 9 The table shows the results of some tests carried out on three solutions, A, B and C.

Sodium Hydrochloric Silver nitrate hydroxide Solution Flame Test acid solution solution is added is added is added

Carbon dioxide gas A Yellow produced

B Brick-red White White precipitate precipitate insoluble in excess sodium hydroxide solution

Dark green C precipitate

Use the information in the table to identify solutions A, B and C.

Give the name of:

(a) solution A; ______(2)

(b) solution B; ______(2)

Immanuel+College Page 17 of 60 A student investigated food dyes using paper chromatography. 10 This is the method used.

1. Put a spot of food colouring X on the start line. 2. Put spots of four separate dyes, A, B, C and D, on the start line. 3. Place the bottom of the paper in water and leave it for several minutes.

Figure 1 shows the apparatus the student used.

Figure 1

(a) Write down two mistakes the student made in setting up the experiment and explain what problems one of the mistakes would cause.

______

______(2)

Immanuel+College Page 18 of 60 (b) Another student set up the apparatus correctly.

Figure 2 shows the student’s results. The result for dye D is not shown.

Figure 2

Calculate the Rf value of dye A

Give your answer to two significant figures.

______

Rf value = ______(3)

______

Distance moved by dye D = ______(1)

Immanuel+College Page 19 of 60 (d) Explain how the different dyes in X are separated by paper chromatography.

______

______(4)

(e) Flame emission spectroscopy can be used to analyse metal ions in solution.

Figure 3 gives the flame emission spectra of five metal ions, and of a mixture of two metal ions.

Figure 3

Use the spectra to identify the two metal ions in the mixture.

______

______(2)

Immanuel+College Page 20 of 60 (f) Explain why a flame test could not be used to identify the two metal ions in the mixture.

______

______(2)

(g) Two students tested a green compound X. The students added water to compound X. Compound X did not dissolve.

The students then added a solution of ethanoic acid to compound X. A gas was produced which turned limewater milky.

Student A concluded that compound X was sodium carbonate. Student B concluded that compound X was copper chloride.

Which student, if any, was correct?

Explain your reasoning.

______

______(4) (Total 18 marks)

Immanuel+College Page 21 of 60 This question is about chemical analysis. 11 (a) A student has solutions of three compounds, X, Y and Z.

The student uses tests to identify the ions in the three compounds.

The student records the results of the tests in the table.

Test

Add Add sodium Add nitric acid hydrochloric Compound Flame test hydroxide and silver nitrate acid and barium solution solution chloride solution

X no colour green precipitate white precipitate no reaction

Y yellow flame no reaction no reaction yellow precipitate

Z no colour brown precipitate no reaction cream precipitate

Identify the two ions present in each compound, X, Y and Z.

X ______

Y ______

Z ______(3)

Immanuel+College Page 22 of 60 (b) A chemist needs to find the concentration of a solution of barium hydroxide. Barium hydroxide solution is an alkali.

The chemist could find the concentration of the barium hydroxide solution using two different methods.

Method 1 • An excess of sodium sulfate solution is added to 25 cm3 of the barium hydroxide solution. A precipitate of barium sulfate is formed.

• The precipitate of barium sulfate is filtered, dried and weighed.

• The concentration of the barium hydroxide solution is calculated from the mass of barium sulfate produced.

Method 2 • 25 cm3 of the barium hydroxide solution is titrated with hydrochloric acid of known concentration.

• The concentration of the barium hydroxide solution is calculated from the result of the titration.

Compare the advantages and disadvantages of the two methods.

______

______(5) (Total 8 marks)

Immanuel+College Page 23 of 60 A student was investigating a magnesium salt, X. 12 The student found that X:

• has a high melting point

• does not conduct electricity

• dissolves in water and the solution conducts electricity.

(a) (i) What is the type of bonding in magnesium salt X?

______(1)

(ii) Explain why solid X does not conduct electricity but a solution of X does conduct electricity.

______

______(2)

(b) The student dissolved X in water.

The student added dilute nitric acid and silver nitrate solution to the solution of X.

A white precipitate was formed.

Salt X contains chloride ions.

Explain why a white precipitate was formed.

______

______(2)

Immanuel+College Page 24 of 60 (c) The student dissolved X in water.

The student added a few drops of sodium hydroxide solution to the solution of X.

A white precipitate was formed.

(i) Salt X contains magnesium ions.

Name two other metal ions that would give a white precipitate when a few drops of sodium hydroxide solution are added.

1. ______

2. ______(2)

(ii) Describe the two further tests the student would have to do to show that salt X contains magnesium ions, and not the two metal ions you identified in part (c) (i).

Give the expected results of each test.

______

______(4) (Total 11 marks)

Immanuel+College Page 25 of 60 In this question you will be assessed on using good English, organising information 13 clearly and using specialist terms where appropriate.

A group of students had four different colourless solutions in beakers 1, 2, 3 and 4, shown in the figure below.

The students knew that the solutions were

• sodium chloride

• sodium iodide

• sodium carbonate

• potassium carbonate

but did not know which solution was in each beaker.

The teacher asked the class to plan a method that could be used to identify each solution.

She gave the students the following reagents to use:

• dilute nitric acid

• silver nitrate solution.

Immanuel+College Page 26 of 60 The teacher suggested using a flame test to identify the positive ions.

Outline a method the students could use to identify the four solutions.

You should include the results of the tests you describe.

______

Extra space ______

______

______(Total 6 marks)

Immanuel+College Page 27 of 60 The colours of fireworks are produced by chemicals. 14

(a) Information about four chemicals is given in the table.

Complete the table below.

Colour produced in Chemical firework

barium chloride green

______carbonate crimson

sodium nitrate ______

calcium sulfate red

(2)

(b) Describe a test to show that barium chloride solution contains chloride ions.

Give the result of the test.

______

______(2)

Immanuel+College Page 28 of 60 (c) A student did two tests on a solution of compound X.

Test 1 Sodium hydroxide solution was added. A blue precipitate was formed.

Test 2 Dilute hydrochloric acid was added. Barium chloride solution was then added. A white precipitate was formed.

The student concluded that compound X is iron(II) sulfate.

Is the student’s conclusion correct?

Explain your answer.

______

______(3) (Total 7 marks)

Immanuel+College Page 29 of 60 Four bottles of chemicals made in the 1880s were found recently in a cupboard during a Health 15 and Safety inspection at Lovell Laboratories.

Sodium carbonate Sodium chloride

Sodium nitrate Sodium sulfate

The chemical names are shown below each bottle.

(a) You are provided with the following reagents:

• aluminium powder

• barium chloride solution acidified with dilute hydrochloric acid

• dilute hydrochloric acid

• silver nitrate solution acidified with dilute nitric acid

• sodium hydroxide solution.

• limewater

• red litmus paper

Immanuel+College Page 30 of 60 (i) Describe tests that you could use to show that these chemicals are correctly named.

In each case give the reagent(s) you would use and state the result.

Test and result for carbonate ions:

______

Test and result for chloride ions:

______

Test and result for nitrate ions:

______

Test and result for sulfate ions:

______

______(4)

(ii) Suggest why a flame test would not distinguish between these four chemicals.

______(1)

(b) Instrumental methods of analysis linked to computers can be used to identify chemicals.

Give two advantages of using instrumental methods of analysis.

______

______(2) (Total 7 marks)

Immanuel+College Page 31 of 60 Low sodium salt is used on food. This label is from a packet of low sodium salt. 16

A student tests the low sodium salt for the substances on the label.

(a) (i) The same test can be used to identify sodium ions and potassium ions.

Describe the test.

Give the result of the test for sodium ions and for potassium ions.

______

______(3)

(ii) It is difficult to identify potassium ions when sodium ions are present.

Suggest why.

______

______(1)

Immanuel+College Page 32 of 60 (b) Describe how the student would test a solution of the low sodium salt for chloride ions.

Give the result of the test.

______

______(3)

(c) To test for magnesium ions, the student adds a few drops of sodium hydroxide solution to a solution of the low sodium salt.

A white precipitate is produced.

This test also gives a white precipitate with aluminium ions and calcium ions.

(i) Describe how the student could confirm that the low sodium salt contains magnesium ions and not aluminium ions.

______

______(2)

(ii) Describe a test the student could do to confirm that the low sodium salt does not contain calcium ions.

______

______(2) (Total 11 marks)

Immanuel+College Page 33 of 60 A student investigated an egg shell. 17

Trish Steel [CC-BY-SA-2.0], via Wikimedia Commons

(a) The student did some tests on the egg shell.

The student’s results are shown in the table below.

Test Observation

A gas was produced. Dilute hydrochloric acid was 1 added to the egg shell. The egg shell dissolved, forming a colourless solution.

A flame test was done on the 2 colourless solution from test 1. The flame turned red.

Sodium hydroxide solution was A white precipitate formed that did not 3 added to the colourless solution dissolve in excess sodium hydroxide from test 1. solution.

Silver nitrate solution was added 4 to the colourless solution from A white precipitate formed. test 1.

(i) The student concluded that the egg shell contains carbonate ions.

Describe how the student could identify the gas produced in test 1.

______

Immanuel+College Page 34 of 60 (2)

(ii) The student concluded that the egg shell contains aluminium ions.

Is the student’s conclusion correct? Use the student’s results to justify your answer.

______

______(2)

(iii) The student concluded that the egg shell contains chloride ions.

Is the student’s conclusion correct? Use the student’s results to justify your answer.

______

______(2)

(b) Some scientists wanted to investigate the amount of lead found in egg shells. They used a modern instrumental method which was more sensitive than older methods.

(i) Name one modern instrumental method used to identify elements.

______

______(1)

(ii) What is the meaning of more sensitive?

______

______(1) (Total 8 marks)

Immanuel+College Page 35 of 60 Ammonium sulfate is an artificial fertiliser. 18

(a) (i) When this fertiliser is warmed with sodium hydroxide solution, ammonia gas is given off. Describe and give the result of a test for ammonia gas.

Test ______

______

Result ______

______(2)

(ii) Describe and give the result of a chemical test to show that this fertiliser contains 2– sulfate ions (SO4 ).

Test ______

______

Result ______

______(2)

(b) Ammonium sulfate is made by reacting sulfuric acid (a strong acid) with ammonia solution (a weak alkali).

(i) Explain the meaning of strong in terms of ionisation.

______(1)

Immanuel+College Page 36 of 60 (ii) A student made some ammonium sulfate in a school laboratory.

The student carried out a titration, using a suitable indicator, to find the volumes of sulfuric acid and ammonia solution that should be reacted together.

Name a suitable indicator for strong acid-weak alkali titrations.

______(1)

(iii) The student found that 25.0 cm3 of ammonia solution reacted completely with 32.0 cm3 of sulfuric acid of concentration 0.050 moles per cubic decimetre.

The equation that represents this reaction is:

2H2SO4(aq) + 2NH3(aq) → (NH4)2SO4 (aq)

Calculate the concentration of this ammonia solution in moles per cubic decimetre.

______

Concentration = ______moles per cubic decimetre (3)

(iv) Use your answer to (b)(iii) to calculate the concentration of ammonia in grams per cubic decimetre.

(If you did not answer part (b)(iii), assume that the concentration of the ammonia solution is 0.15 moles per cubic decimetre. This is not the correct answer to part (b)(iii).)

Relative formula mass of ammonia (NH3) = 17.

______

Concentration = ______grams per cubic decimetre (2) (Total 11 marks)

Immanuel+College Page 37 of 60 (a) Four bottles of chemicals made in the 1880s were found recently in a cupboard during a 19 Health and Safety inspection at Lovell Laboratories.

The chemicals are correctly named.

You are provided with the following reagents:

• aluminium powder

• barium chloride solution acidified with dilute hydrochloric acid

• dilute hydrochloric acid

• silver nitrate solution acidified with dilute nitric acid

• sodium hydroxide solution.

Immanuel+College Page 38 of 60 (i) Describe tests to show that these chemicals are correctly named.

In each case give the reagent(s) you would use and state what you would see.

Test and result for carbonate ions:

______

Test and result for chloride ions:

______

Test and result for nitrate ions:

______

Test and result for sulfate ions:

______

______(5)

(ii) Suggest why a flame test would not distinguish between these four chemicals.

______(1)

(b) Instrumental methods of analysis linked to computers can be used to identify chemicals.

Describe two advantages of using instrumental methods of analysis.

______

______(2) (Total 8 marks)

Immanuel+College Page 39 of 60 Mark schemes

(a) (i) fizz / effervescence / bubbles 1 allow calcium carbonate decreases in size or dissolves 1

because carbon dioxide produced / released allow because gas produced / released 1

limewater turns cloudy / milky / white 1

because (a precipitate of or solid) calcium carbonate forms allow because of carbon dioxide if not already credited 1

(ii)

allow -OH do not allow lower case ‘h’ 1

(iii) acid must be in this order ignore any name of an acid 1

ester(s) 1

(b) white (precipitate) no change

no change no change

all four correct 2 marks any two correct 1 mark 2

red 1 must be in this order

(ii) colours are masked / changed by each flame colour 1 [12] Immanuel+College Page 40 of 60 (a) (i) carbon dioxide / CO2 2 1

2- carbonate / CO3 answers must be in the order shown marks are independent 1

(ii) ammonia / NH3 1

litmus answers must be in the order shown marks are independent 1

(b) (i) solution is blue accept blue precipitate only if sodium hydroxide added allow blue liquid allow copper sulfate / copper ions are blue 1

(ii) barium chloride / BaCl2 allow barium nitrate / barium ions / Ba2+ 1

white answers must be in the order shown marks are independent 1 [7]

(a) limewater / calcium hydroxide 3 1

(limewater) goes milky / cloudy do not allow this mark if lime water added to solution or powder

gives white precipitate / solid 1

(b) eg flame colour of (Na) and flame colour of (K) interfere / mask / mix with each other accept difficult to determine the colour or hard to distinguish accept some indication that two distinct colours are not seen 1

Immanuel+College Page 41 of 60 (c) (i) barium chloride (solution) / BaCl2 ignore mention of acidification but do not allow sulfuric acid. wrong reagent = no mark 1

white precipitate / white solid allow white barium sulfate or barium sulfate precipitate 1

(ii) white precipitate / white solid ignore goes milky do not accept any mention of precipitate dissolving 1 [6]

(a) (i) it = copper 4 (copper) stops barnacles / seaweed (sticking) accept lead doesn’t stop barnacles / seaweed (sticking) ignore all other properties 1

(ii) it = Muntz Metal

(Muntz Metal) is less expensive / cheaper / cheapest must be a comparison accept copper is more expensive ignore other properties 1

(b) (i) atomic absorption spec(troscopy) / spectrometry or mass spec(trometry) / spectroscopy accept spectroscopy / spectrometry alone allow AAS / MS do not allow NMR spectroscopy or IR spectrometry or chromatography 1

(ii) it = instrumental method

sensitive or detect (very) small amounts or only small sample needed allow (more) precise ignore accurate allow converse for chemical method ignore metal contains small amount / low concentration of iron 1

Immanuel+College Page 42 of 60 (c) any two from: transition elements (= they)

• unreactive / not very reactive allow does not corrode ignore reference to rust

• strong / hard ignore tough / durable / hard wearing

• malleable / easy to shape ignore ductile / density / melting point 2 [6]

(a) (acidified) barium chloride / nitrate 5 incorrect reagent or no reagent = 0 marks do not accept acidified with sulfuric acid (still allow result mark if correct) allow solution of barium ions / salt not barium solution do not accept barium hydroxide 1

(white) precipitate / solid do not accept incorrect colour for precipitate allow barium sulfate (formed) ignore ‘it goes white / cloudy’ 1

(b) (white) precipitate / solid allow aluminium hydroxide (formed) do not allow incorrect colour for precipitate 1

(precipitate) dissolves (in excess) allow sodium aluminate (formed) allow goes clear / colourless if incorrect colour precipitate then allow dissolves (in excess) 1

Immanuel+College Page 43 of 60 (c) any two from: apply list principle

• yellow = sodium (alum) allow orange or yellow orange

• lilac = potassium (alum) allow purple

• colourless = ammonium (alum) if no colours given, allow ‘different coloured flames’ for 1 mark 2 [6]

(a) (i) hydrochloric acid / HCl 6 accept any (named) acid 1

carbon dioxide / CO2 accept bubbles / fizz / gas or limewater gets milky ignore ‘add limewater’ do not accept other named gases 2nd mark dependant on first mark

accept for this answer only heat gives CO2 / limewater milky = 1 mark 1

(ii) (white) precipitate / solid ignore names of substances even if incorrect accept white deposit / substance do not accept any coloured precipitate 1

(iii) eg flame colour of (Na) and flame colour of (K) interfere / mask / mix with each other accept ‘can’t see the colours’ or ‘difficult to determine the colour’ or ‘both produce different colours’ or a correct statement of colours or hard to distinguish 1

(b) (i) eg essential (mineral) or everyone needs it / some (salt) or problems with health if have no salt accept preservative / flavouring / taste it = salt (all) foods contain / use it / sodium chloride / salt 1

Immanuel+College Page 44 of 60 (ii) mark positively ie no list principle

advantages

any two from: ignore economic arguments throughout or people eat less salt

• more people will be healthier

• (should have) less heart disease

• (should have) less cancer

• (more people with) lower blood pressure 2

disadvantages

any one from: ignore references to too much / too little (salt)

• not everyone affected

• not enough evidence

• does not provide choice

• undemocratic

• less taste / flavour ignore no flavour / taste

• shorter shelf life / not preserved (as long) ignore references to sell by dates

• too much potassium chloride might be bad 1 [8]

(a) (i) red / brick-red / orange-red / red-orange 7 allow red-brown or brown-red do not accept orange alone eg ‘red or orange’ = 0 1

(ii) sodium allow sodium compounds ignore incorrect symbol

or Na / Na+ if symbol alone given do not accept Na2+ or Na– 1 Immanuel+College Page 45 of 60 (iii) any one from

• accurate / sensitive

• use small amounts

• fast / quick / rapid

• ease of automation

• reliable / efficient

• operatives do not need chemical skills ignore cost / safety / human error or ease of use or shows all the elements 1

(iv) (atomic absorption) spectroscopy or (mass) spectrometry accept AAS / aas or mass spec accept atomic absorption ignore ms / MS do not allow UV / IR / NMR / chromatography / GLC 1

Immanuel+College Page 46 of 60 (b) any three from:

• (safe because) similar to mothers. milk allow calcium carbonate is in breast milk allow some mothers unable to breast feed ignore ‘recommended’ alone

• babies (in developing world) would die accept causes malnutrition

• if banned there would be a cost involved allow it is free

• it is not a pollutant / harmful / dangerous accept not all chemicals are pollutants / harmful / dangerous

• not mass medication

• not just used for gravestones allow it has many uses ignore only small amounts of it or it occurs naturally

• (calcium carbonate) is needed for bones / teeth / health allow ‘essential mineral’

• Mrs Right has a personal interest or not impartial or distorts information / bias or she is paid by a charity accept ‘it is (only) her opinion’ 3 [7]

(a) kills bacteria / sterilises (water) 8 allow kills microorganisms / microbes / germs allow ‘makes (water) safe (to drink)’ or disinfectant ignore cleans water or removes impurities / bacteria 1

(b) goes colourless / decolourised (from red / red-brown / brown / yellow / orange) allow colour disappears ignore ‘goes clear’ or discoloured do not accept incorrect initial colour do not accept precipitate 1

– (c) (i) Br2 and 2Cl allow multiples / fractions if whole equation balanced 1

Immanuel+College Page 47 of 60 (ii) changes to red / red-brown / brown / yellow / orange do not accept effervescence / fizzing / precipitate / gas given off ignore vapour / temperature changes / ignore initial colour 1

(d) (i) 7 outer electrons or

same number of outer electrons allow last / final shell for outer allow energy level / orbit / ring for shell allow ‘need to gain 1 e – to have a full outer shell’ ignore ‘similar number of outer electrons’ 1

(ii) bromine / it (atom) is bigger or must be a comparison

outer electrons (level / shell) further from nucleus or more shells do not accept more outer shells ignore more electrons

forces / attractions are weaker or more shielding or attracts less do not accept magnetic / gravitational / intermolecular forces allow ‘electron(s) attracted less easily’

electron(s) gained less easily “outer / last / final” must be mentioned once, otherwise max 2 marks. accept converse for chlorine throughout where clearly stated 3

(e) (i) white precipitate or white solid ignore names of chemicals 1

(ii) cream precipitate or cream solid allow pale yellow / off-white precipitate / solid ignore names of chemicals 1 [10]

(a) sodium carbonate / sodium hydrogencarbonate / sodium bicarbonate 9 Na2CO3 / NaHCO3 ie sodium / sodium ions (1 mark) carbonate / carbonate ions (1 mark) incorrect formula including Na and CO3 = 1 mark 2

Immanuel+College Page 48 of 60 (b) calcium chloride

CaCl2 ie calcium / calcium ions (1 mark) chloride / chloride ions (1 mark) incorrect formula including Ca and Cl = 1 mark 2

(c) iron or iron(II) ions Fe2+ ferrous ions ignore anions ignore nickel / chromium do not accept iron(III) or ferric ions5 1 [5]

(a) water level above the start line 10 and start line drawn in ink allow water level too high 1

water level food colours would dissolve into water or start line the ink would ‘run’ on the paper 1

(b) (distance moved by A) 2.8cm and 8.2 cm (distance moved by solvent) allow values in range 2.7 − 2.9 cm and 8.1 − 8.3 cm 1

0.34 allow 0.33 or 0.35 allow ecf from incorrect measurement to final answer for 2 marks if given to 2 significant figures accept 0.34 without working shown for 3 marks 1

(d) solvent moves through paper 1

different dyes have different solubilities in solvent 1

Immanuel+College Page 49 of 60 and different attractions for the paper 1

and so are carried different distances 1

(e) calcium ions allow Ca2+ 1

sodium ions allow Na+ 1

(f) two different colours or Ca2+ / one is orange-red and Na+ / the other is yellow allow brick red for Ca2+ and / or orange for Na+ allow incorrect colours if consistent with answer to 7.5 1

(so) colours mix or (so) one colour masks the other 1

(g) (Student A was incorrect) because sodium compounds are white not green or because sodium carbonate is soluble 1

so can’t contain sodium ions 1

(Student B was incorrect) because adding acid to carbonate produces carbon dioxide 1

so must contain carbonate not chloride ions 1 [18]

(a) X: 11 2+ 2- Fe / iron(II), SO4 / sulfate allow iron(II) sulfate or FeSO4 1

Y: Na+ / sodium, I- / iodide allow sodium iodide or NaI 1

Immanuel+College Page 50 of 60 Z: Fe3+ / iron(III), Br- / bromide allow iron(III) bromide or FeBr3 correct identification of any two ions = one mark correct identification of any four ions = two marks 1

(b) any five from: allow converse arguments

method 1

• weighing is accurate • not all barium sulfate may be precipitated • precipitate may be lost • precipitate may not be dry • takes longer • requires energy allow not all the barium hydroxide has reacted

method 2 • accurate • works for low concentrations allow reliable / precise 5 [8]

(a) (i) ionic (bonding) 12 1

(ii) ions cannot move in solid or are in fixed positions do not accept electrons / atoms / molecules ignore particles must mention ions 1

but can move in solution 1

(b) silver chloride formed 1

which is insoluble 1

calcium accept other metal ions that also give white precipitates (such as lead and zinc) 1

Immanuel+College Page 51 of 60 (ii) add excess sodium hydroxide solution the second mark of each pair is dependent on the first mark being awarded. 1

precipitate remains 1

carry out a flame test 1

not red / orange accept any colour that is not orange / red give full credit for answers that correctly eliminate other cations in (c)(i) that would give white precipitates with a few drops of NaOH 1 [11]

Immanuel+College Page 52 of 60 Marks awarded for this answer will be determined by the Quality of Communication (QC) as well 13 as the standard of the scientific response. Examiners should also apply a ‘best-fit’ approach to the marking.

0 marks No relevant content

Level 1 (1 – 2 marks) Any description of a method used and / or a result given

Level 2 (3 – 4 marks) Description of workable methods used, with results to identify positive or negative ions

Level 3 (5 – 6 marks) Description of methods used to identify both positive and negative ions, with relevant results

examples of the points made in the response extra information

Test: add (platinum / nichrome) wire (for the flame test) accept any method of introducing the solution into the flame, eg a splint soaked in the solution or sprayed from a bottle

Result: the sodium compounds result in a yellow / orange / gold flame or the potassium compound results in a lilac / purple / mauve flame student could state that potassium carbonate gives a different colour to the three sodium compounds as long as it is clear that the flame test colour comes from Na+ or K+

Test: add dilute nitric acid to all four solutions allow any acid

Result: sodium carbonate and potassium carbonate will effervesce or sodium chloride and sodium iodide will not effervesce

Test: add dilute nitric acid followed by silver nitrate

Result: sodium chloride and sodium iodide produce a precipitate or sodium chloride produces a white precipitate and sodium iodide produces a yellow precipitate accept sodium carbonate and potassium carbonate do not produce a precipitate [6]

Immanuel+College Page 53 of 60 (a) lithium 14 allow Li+ / Li 1

yellow allow orange 1

(b) silver nitrate (solution) incorrect test = 0 marks ignore (nitric) acid do not allow other named acids 1

white precipitate 1

and white precipitate (with barium chloride) indicates sulfate ions 2- allow SO4

accept compound X is copper sulfate / CuSO4 for 1 mark 1

but iron(II) ions produce a green precipitate (with sodium hydroxide) 1 [7]

(a) (i) Na CO : HCl → gas / effervescence / bubbles (1) 15 2 3 CO2 / carbon dioxide / turns lime water milky (1) 1

NaCl: AgNO3 → white ppt (1) silver chloride (1) 1

NaNO3: Al + NaOH → pungent / sharp smell / choking gas (1) NH3 / ammonia / turns (red) litmus blue(1) 1

Na2SO4: BaCl2 → white ppt (1) barium sulfate (1) 1 each correct test and one result = 1 mark one other result for any test = 1 mark this mark can only be awarded once

Immanuel+College Page 54 of 60 (ii) all would give a yellow / yellow-orange (flame) / same coloured (flame) / same results allow orange (flame) 1

they all contain sodium 1

(b) any two from: ignore cost/errors

• fast / quick or comment about speed allow precise

• small amounts/sensitive allow can be left to run/continuous analysis

• accurate

• ease of automation accept operators do not need chemical skills

• sample not used up

• reliable / efficient 2 [7]

(a) (i) place sample in flame 16 accept flame test accept any workable method allow burn ignore heat 1

sodium: yellow (flame) allow orange 1

potassium: lilac (flame) allow purple 1

(ii) (lilac) colour (of potassium) obscured by (yellow) colour of sodium

allow difficult to see two colours allow sodium colour is brighter allow colours mix 1

Immanuel+College Page 55 of 60 (b) acidify (with nitric acid) do not accept if acidified with anything other than nitric acid 1

add silver nitrate (solution) 1

white precipitate depends on second marking point allow white solid ignore silver chloride ignore solution goes cloudy / milky 1

aluminium (ions / hydroxide (re)dissolve depends on first marking point allow if aluminium, (white) precipitate / solid dissolves allow magnesium (ions / hydroxide) do not (re)dissolve 1

(ii) place sample in flame accept flame test accept any workable method allow burn ignore heat 1

flame does not go red accept calcium (ions / hydroxide would produce) red flame allow magnesium (ions / hydroxide) (produce) no flame colour 1 [11]

(a) (i) (bubble gas produced through) limewater 17 incorrect tests = zero 1

(limewater) goes cloudy / milky 1

(ii) ignore yes or no

red flame indicates that calcium / lithium ions present allow aluminium has no flame colour

Ca/Mg also produce a (white) precipitate with NaOH 1

Immanuel+College Page 56 of 60 the (white) precipitate formed in test 3 or by adding sodium hydroxide solution would dissolve (in excess) if aluminium ions were present 1

(iii) ignore yes or no

because a white precipitate is formed in test 4 or by adding silver nitrate 1

but chloride ions are in hydrochloric acid 1

(b) (i) mass spectrometry allow MS

atomic absorption spectroscopy allow AAS spectrometry / spectroscopy alone is insufficient 1

(ii) can detect a small(er) amount of the substance allow can detect small(er) changes allow small(er) sample sizes ignore references to precision / accuracy 1 [8]

(a) (i) incorrect test or no test = 0 mark 18 testing the solution or using blue litmus = 0 mark

(test ammonia / gas with red) litmus accept any acid-base indicator with correct result 1

(goes) blue

(conc.) HCl (1)

white fumes / smoke / solid (1) allow white gas / vapour

(test ammonia / gas with) Universal Indicator (1)

blue / purple (1) 1

Immanuel+College Page 57 of 60 (ii) incorrect test or no test = 0 marks

add barium chloride / BaCl2 (solution)

do not accept H2SO4 added

or add barium nitrate / Ba(NO3)2 (solution) allow Ba2+ solution / aqueous added 1

white precipitate / solid (formed)

allow white barium sulfate / BaSO4

ignore barium sulfate / BaSO4 alone 1

(b) (i) fully / completely ionised / dissociated or hydrogen ions fully dissociated accept has more ions than weaker acid / alkali of same concentration ignore strongly ionised do not accept ions are fully ionised ignore concentrated or reference to concentrations of ions 1

(ii) methyl orange accept correct spelling only accept any strong acid-weak base indicator do not allow phenolphthalein / litmus / universal indicator 1

(iii) 32 × 0.05/1000 or 0.0016 (mole H2SO4 ) accept (0.05 x 32) = (V x 25) or 0.05 x 32 / 25 1

3 (reacts with) 2 × 0.0016 or 0.0032 (mole NH3 in 25 cm ) accept dividing rhs by 2 or multiplying lhs by 2 1

(0.0032 × 1000/25 =) 0.128 allow ecf from previous stage correct answer 0.128 or 0.13 with or without working gains all 3 marks 1

Immanuel+College Page 58 of 60 (iv) 2.176 or 2.18 correct answer with or without working

or ecf from candidate’s answer to (b)(iii)

or 2.55 if 0.15 moles used if answer incorrect or no answer 0.128 × 17 or 0.13 x 17 or their (b)(iii) × 17 or 0.15 × 17 gains 1 mark 2 [11]

(a) (i) each correct test and one result = 1 mark 19 one other result for any test = 1 mark this mark can only be awarded once 1

Na2CO3: HCl → (odourless) gas (1) CO2 / carbon dioxide (1) 1

NaCl: AgNO3 → white ppt (1) silver chloride (1) 1

NaNO3: Al + NaOH → pungent /sharp smell / choking gas (1) NH3 / ammonia (1) 1

Na2SO4: BaCl2 → white ppt (1) barium sulphate (1) 1

(ii) all would give a yellow / yellow-orange (flame) / same coloured (flame) / same results allow orange (flame)

they all contain sodium owtte 1

Immanuel+College Page 59 of 60 (b) any two from: ignore cost

• fast / quick or comment about speed ignore human error

• small amounts accept any valid answer

• sensitive / accurate accept operators do not need chemical skills

• ease of automation

• sample not used up

• reliable / efficient

• can be left to run / continuous analysis ignore results can be saved 2

Immanuel+College Page 60 of 60