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School of Chemistry

UNIVERSITY OF KWAZULU-NATAL, HOWARD COLLEGE JUNE 2010 EXAMINATION CHEM100: SPECIAL SCIENCE – CHEMISTRY

DURATION: 2 HOURS TOTAL MARKS: 100

Internal Examiners: Dr K B Brookes

External Examiner: Dr B Moodley

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Notes: This paper consists of 15 pages including an appendix and periodic table at the end. Please check that you have them all. Answer ALL questions on the question paper. Show ALL calculations. Calculators may be used.

Question Maximum Internal Mark External Mark 1 20 2 20 3 20 4 15 5 25 Total 100

Students are requested, in their own interest, to write legibly.

QUESTION 1 UNITS AND PROPERTIES OF MATTER (20 Marks) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 2

1.1 a) What is the SI unit for temperature? (1)

b) The melting point for cholesterol is 148.5 oC. Express this m.p. in: i) K (1)

ii) oF (2)

1.2 a) An unknown substance has a mass of 5.00 g and a volume of 100 ml. Calculate the density of this substance. (2) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 3

1.2 b) Assuming this substance is insoluble in alcohol, would you expect it to sink or float in alcohol (alcohol has density 0.80 g/ml)? (1)

1.3 a) Define clearly what is meant by a compound. (2)

b) In what way does a mixture differ from a pure compound? (1)

1.3 c) Give an example of any mixture. (1)

1.4 a) State the law of Conservation of Matter. (1)

b) Which of the 3 states of matter has the highest kinetic energy? (1)

1.4 c) Give an example of a device that depends on kinetic energy to function. (1) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 4

1.5 a) How many kilocalories of energy should an adult “burn” at the gym to lose 0.5 kg of body fat? (2)

b) If an adult uses up 500 k.cal energy per hour exercising, how long will it take to lose the above mass of body fat? (1)

c) Distinguish between endothermic and exothermic reactions. (2)

d) Give an example of a highly electronegative element. (1) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 5

QUESTION 2 ATOMS, BONDING AND REACTIONS (20 Marks)

2.1 A neutral isotope of an element has 33 electrons and mass number 75. Supply the following: (3) a) Atomic Number

b) Number of neutrons

c) Name or symbol of the element

2.2 Supply examples of the following: (3)

a) A compound which is a good oxidizing agent.

b) An element which is a gas.

c) An element which is a liquid metal.

2.3 Balance the following redox equation for a car battery. Write the oxidation number above every atom that is oxidised or reduced: (4)

Pb + PbO2 + H2SO4 → PbSO4 + H2O

2.4 a) How do isotopes of the same element differ from each other? (1)

2.4 b) List 2 ways that medical staff can protect themselves from radiation from School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 6

radioisotopes. (2)

c) 131I has a half-life of 8 days. If a dose of 16 mg is given to a patient, how much radioactive 131I will remain in the patient’s body after 24 days? (2)

d) Discuss how Boron Neutron Capture Therapy is used to destroy cancerous cells. (3)

2.5 a) Write the structure of a simple cation which is commonly found in body fluids. (1) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 7

2.5 b) Write the formula for the phosphate ion. (1)

QUESTION 3 GASES, SOLUTIONS AND EMULSIONS (20 marks)

3.1 a) State Charles Law for gases. (2)

b) A sample of CO2 gas with a pressure of 55 mmHg in a volume of 125 ml is placed in a new flask. The pressure of the gas in the new flask is 78 mmHg. What is the volume of the new flask? (The temperature remains constant). (3)

3.2 a) List two conditions for which treatment with hyperbaric oxygen could be beneficial for a patient. (2) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 8

3.2 b) Give a medical use for each of the following gases: (2)

i) CO2

ii) NO

3.3 Drugs may be given in the form of solutions, suspensions or emulsions. List the general properties for each of these forms. (3)

3.4 Solution A, containing 0.9% NaCl, is isotonic with blood. Solution B is made up by dissolving 70 mg of NaCl in 10 cm3 of water. Is solution B isotonic, hypotonic or hypertonic compared to solution A? Show your calculations. (4) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 9

3.5 Explain how you would prepare a one litre solution of 5% KCl by diluting from a stock solution of 15% KCl. Show your calculations. (4)

QUESTION 4 ACIDS, BASES AND SALTS (15 marks)

4.1 Define the following:

a) a base (1)

b) neutralisation (2)

4.2 Classify each of the following acids as weak or strong: (2)

a) Carbonic acid, H2CO3

b) Hydrochloric acid, HCl School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 10

4.3 List one use in medicine for each of the following salts or acids: (4)

a) HOCl (hypochlorous acid)

b) H3BO3 (boric acid)

c) NH4Cl (ammonium chloride)

d) (CaSO4)2.H2O (calcium sulfate)

4.4 a) Explain the role of a buffer such as carbonic acid and sodium bicarbonate in maintaining the correct pH for body fluids. (2)

4.4 b) Define the condition called acidosis. (2) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 11

c) Suggest a possible cause for acidosis. (1)

4.5 What is the approximate pH of gastric juice (stomach acid)? (1)

QUESTION 5 ORGANIC CHEMISTRY (25 marks)

5.1 a) What is meant by 1) saturated and 2) unsaturated organic compounds? (2)

b) Give and example of i) an alkene

ii) an alkyne (2)

5.2 What is the functional group for: School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 12

a) an alcohol? (1)

b) an amine? (1)

5.3 What are the general characteristics of heterocyclic compounds such as pyrrole or pyridine? (2)

5.4 a) What are the general chemical characteristics of all carbohydrates? (2)

b) Draw the straight chain form of glucose. (2) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 13

5.4 c) What is glucose oxidized to in the chemical test for urine using an alkaline solution of Cu2+ ions (Benedict’s solution)? (1)

d) What is the reddish-brown reduction product from the above reaction? (1)

e) Name the carbohydrate known as “milk sugar” (1)

5.5 a) List 2 fat-soluble vitamins and give the medical conditions that results for each one if it is deficient in the diet. (4)

5.5 b) Give and example of: School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 14

i) a saturated fatty acid (1)

ii) an unsaturated fatty acid (1)

5.6 a) Proteins are macromolecules. What class of compounds is the building- block for proteins? (1)

b) Name the process by which the 3D structure of a protein is destroyed. (1)

c) List 2 factors that may cause the above process to occur. (2) School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 15 School of Chemistry, University of KwaZulu-Natal, Howard College June 2010 Examination CHEM100: Special science (Chemistry) Page 16