THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL OF TANZANIA

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION

032/1 CHEMISTRY 1

(For Both School and Private Candidates)

TIME: 3 Hours 2006/10/10 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. All questions carry equal marks.
4. Cellular phones are not allowed in the examination room.
5. Electronic calculators are not allowed in the examination room.
6. Write your Examination Number on every page of your answer booklet(s).
7. In your calculations you may use the following constants:

• Atomic masses:
• H = 1, C = 12, O = 16, Na = 23, N = 14, Mg = 24, S = 32, Ca = 40, Ar = 40, K = 39.
• Avogadro's constant = 6.02 × 10²³
• ^{G.M.V. at s.t.p. = 22.4 dm3}
• 1 Faraday = 96500 Coulombs.
• Standard temperature = 273 K.
• Standard pressure = 760 mmHg.
• 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. Addition of sulphate of ammonia to the soil corrects the deficiency of

1. oxygen and nitrogen
2. nitrogen and hydrogen
3. nitrogen and sulphur
4. sulphur and oxygen
5. sulphur and hydrogen

ii. When substances A and B react to form a new substance C the reactants A and B are said to

1. undergo a chemical change
2. form a solution C
3. undergo a physical change
4. form a mixture
5. undergo dissociation

iii. When an alcohol reacts with a carboxylic acid they form an organic compound called

1. an alkyne
2. an ester
3. a haloalkane
4. an alkene
5. an alkane

iv. The reaction between iodine and hydrogen is represented by the equation I₂ + H₂ → 2HI   ΔH = −x kJmol⁻¹. This shows that the reaction is

1. an endothermic reaction
2. a replacement reaction
3. a neutralization reaction
4. a thermal decomposition reaction
5. an exothermic reaction

v. A molar solution was found to have a pH of 5. The most correct explanation about the solution is, thus, a

1. base
2. neutral
3. very strong base
4. acid
5. very weak base

vi. A solution of sodium carbonate was prepared in order to get a 2 M solution. 200 cm³ of this solution was used in a titration experiment. The number of mole(s) present in 200 cm³of 2 M solution used in the titration will be

1. 4.0
2. 0.04
3. 0.45
4. 0.045
5. 0.40

vii. The net ionic equation for the reaction between ammonium chloride and sodium hydroxide solution on warming is

1. H⁺ + OH⁻ → H₂O
2. NH₄⁺ + OH⁻ → NH₃ + H₂O
3. Na⁺ + Cl⁻ → NaCl
4. 2NH₄ + 2OH⁻ → 2NH₃ + Cl₂ + H₂
5. NH₃ + H₂O → NH₄OH

viii. Alkynes are organic compounds whose homologous series has a general molecular formula of

1. C_nH_2n
2. C_nH_(2n+2)
3. C_nH_(2n−2)
4. C_nH_(2n+1)
5. C_nH_(n+2)

ix. When chlorine gas is passed through a green solution of iron (II) chloride, it changes its colour from green to yellowish brown because

1. Fe²⁺ ions were oxidized to Fe³⁺
2. Fe³⁺ ions were reduced to Fe²⁺
3. Fe²⁺ ions were reduced to Fe³⁺
4. Fe³⁺ ions were oxidized to Fe²⁺
5. Fe²⁺ ions were reduced to Fe

x. An element with atomic number 10 is likely to have chemical properties which are similar to the properties of an element whose atomic number is

1. 9
2. 16
3. 20
4. 22
5. 18