THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

032/1 CHEMISTRY 1

(For Both School and Private Candidates)

Time: 3 Hours Tuesday, October 11, 2005 p.m.

Instructions

1. This paper consists of sections A, B and C.
2. Answer all questions in sections A and B and two (2) questions from section C.
3. Electronic calculators are not allowed in the examination room.
4. Cellular phones are not allowed in the examination room.
5. Write your Examination Number on every page of your answer booklet(s).
6. The following constants may be used:
   
   Atomic masses: H = 1; C = 12; O = 16; Cu = 64; Ca = 40; Na = 23; S = 32; Cl = 35.5; Fe = 56; N = 14; K = 39.
   Avogadro’s Number = 6.02 × 10²³.
   GMV at s.t.p. = 22.4 dm³.
   1 Faraday = 96500 coulombs.
   1 litre = 1 dm³ = 1000 cm³

SECTION A (20 marks)

Answer all questions in this section.

1. For each of the items (i) - (x) choose the correct answer from among the given alternatives and write its letter beside the item number.

(i) Sodium metal is kept in oil because it

1. sinks in oil but floats in water
2. reacts vigorously with water
3. is very alkaline
4. forms a protective coat of sodium oxide with oil
5. forms a protective coat of sodium oxide with water

(ii) A gas burned in air forms carbon dioxide and water only. From this experiment the gas is likely to be

1. hydrogen
2. carbon monoxide
3. ethane
4. nitrogen
5. ozone

(iii) The molarity of a solution containing 26.5 g of anhydrous sodium carbonate in 5 dm³ of the solution is _____ M.

1. 0.05
2. 0.25
3. 1.25
4. 3.50
5. 0.025

(iv) It was found that 32.7 g of zinc metal displaces 108 g of silver metal from an aqueous solution of silver nitrate. The correct equation for this reaction is

1. Zn²⁺_(aq) + Ag_(s) → Ag⁺_(aq) + Zn_(s)
2. Zn_(s) + Ag⁺_(aq) → Ag_(s) + Zn²⁺_(aq)
3. Zn²⁺_(aq) + 2Ag⁺_(aq) → 2Ag_(s) + Zn²⁺_(aq)
4. Zn²⁺_(aq) + 2Ag⁺_(aq) → 2Ag⁺_(aq) + Zn_(s)
5. Zn_(s) + 2Ag⁺_(aq) → Zn²⁺_(aq) + 2Ag_(s)

(v) The pair of elements which is most likely to form a covalent bond when reacted together is

1. sodium and iodine
2. magnesium and oxygen
3. aluminium and oxygen
4. carbon and chlorine
5. calcium and carbon

(vi) The method of collecting hydrogen chloride gas in a class experiment is known as

1. downward displacement of water
2. downward displacement of air
3. upward displacement of air
4. fountain
5. condensation

(vii) Sea water contains various salts, which salt is present in the greatest proportion?

1. magnesium chloride
2. calcium sulphate
3. potassium chloride
4. sodium chloride
5. magnesium sulphate

(viii) When dilute solutions of calcium chloride and sodium carbonate are mixed,

1. a white precipitate of sodium chloride is formed
2. carbon dioxide is evolved
3. a mixture of precipitates of sodium chloride and calcium carbonate is formed
4. a white precipitate of calcium carbonate is formed
5. a colourless solution of calcium carbonate and sodium chloride is formed

(ix) The atomic number of elements chlorine, argon and potassium are 17, 18 and 19 respectively. Which statement best describes the three elements? These elements

1. have the same number of protons
2. have the same atomic mass
3. occur in the same period
4. have the same number of electrons
5. have octet stable electronic configuration

(x) Three test tubes of the same volume separately contain nitrogen dioxide (NO₂), hydrogen (H₂) and carbon dioxide (CO₂) gases at room temperature and pressure. Then, there

1. is the same number of atoms in each test tube
2. is the same number of molecules in each test tube
3. are more molecules of hydrogen gas than nitrogen dioxide and carbon dioxide molecules
4. is a 3 : 4 : 2 ratio for the number of molecules of carbon dioxide to nitrogen dioxide to hydrogen respectively
5. is a 2 : 4 : 3 ratio of the number of molecules of carbon dioxide to nitrogen dioxide to hydrogen respectively