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 Year: 2022

Instructions

1. This paper consists of sections A, B and C with a total of fourteen (14) questions.
2. Answer all questions in sections A and B and one (1) question from section C.
3. Section A and C carry fifteen (15) marks each and section B carries seventy (70) marks.
4. Non - programmable calculators may be used.
5. Cellular phones and any unauthorised materials are not allowed in the examination room.
6. Write your Examination Number on every page of your answer booklet(s).
7. The following constants may be used.

• Atomic masses: H = l, C = 12, N =14, O =16, Na =23.
• Avogadro's number 6.02 x 10²³ GMV at s.t.p 22.4 dm³ .
• 1 Faraday = 96,500 coulombs.
• 1 litre I= 1m³ = 1000 cm³.

SECTION A (15 Marks)

Answer all questions in this section.

l. For each of the items (i) - (x), choose the correct answer from the given alternatives and write its letter beside the item number in the answer booklet provided.

(i) Which is a chemical property of water?

1. It is a very good solvent.
2. It is neither acidic nor basic.
3. It has higher surface tension.
4. It can exist in three states of matter.
5. It expands when it freezes

(ii) What is the maximum number of electrons in the innermost shell of atoms?

1. 3
2. 1
3. 4
4. 2
5. 8

(iii) What feature is essential for a good fuel?

1. High speed of continuous energy supply.
2. High energy value supplied.
3. Low carbon dioxide supplied.
4. High carbon dioxide production.
5. High content of non-combustible material.

(iv) What conclusion can be drawn from the random movement of pollen grains suspended in air?

1. Matter is lighter in nature.
2. Matter is solid in nature.
3. Matter is particulate in nature.
4. Matter is gaseous in nature.
5. Matter is wave in nature.

(v) Which energy source that can be reused after being exploited?

1. Combustible source.
2. Non-renewable source.
3. Renewable source.
4. Synthetic source.
5. Natural source.

(vi) Which one is the molecular formula for prop-I -ene?

1. C₃H₅
2. CH₃CCH
3. C₃H₄
4. HCH₂CCH
5. CH₃CHCH₂

(vii) Which of the following is not a component of the First Aid Kit?

1. Goggles
2. A pair of scissors
3. Knife
4. Gloves
5. Razor blade

(viii) Which element is oxidised in the following reaction?

2FeSO₄ +CI₂ +H₂SO₄ → Fe(SO₄)₃+ 2HCl.

1. Chlorine
2. Hydrogen
3. Oxygen
4. Sulphur
5. Iron

(ix) Which of the following are the components needed to start fire?

1. Match box, fire wood and kerosene
2. Match box, fire wood and oxygen
3. Oxygen, fuel and fire wood
4. Oxygen, heat and match box
5. Oxygen, fuel and heat

(x) Why is nitrogen formed first during the fractional distillation of air?

1. It has got high boiling point.
2. It has got low density.
3. It has got low melting point.
4. It has got high density.
5. It has got low boiling point.

2. Match the effects on the rate of chemical reactions in List A with the corresponding physical conditions in List B by writing the letter of the correct response beside the item number in the answer booklet provided.

SECTION B (70 Marks)

Answer all questions in this section.

3. (a) How useful is matter in our daily life? Give four points with an example for each.

(b) Why are the chemical symbols important in Chemistry? Give three reasons.

4. Zinc granules were placed in a beaker containing excess dilute sulphuric acid standing on a direct reading balance. The mass of the beaker and its contents were recorded after every two seconds as shown in Table l .

Table 1

(a) Why there was a loss in mass?

(b) Why did the mass remain constant after the eight seconds?

(c) Briefly explain what would happen to the rate of reaction if zinc powder was used instead of granules.

5. A certain compound with the molecular mass of 28 was analyzed and found to be composed of 0.6 g of carbon and 0.1 g of hydrogen.

(a) Work out its empirical formula and molecular formula.

(b) Classify the compound to its homologous series.

6. A Form Three student prepared an experiment to prepare a gas in the laboratory by decomposing a compound using electricity. A steady current was allowed to flow through the solution for 3 hours. At s.t.p 4.12 dm³ of the gas which relighted the glowing splint was produced.

(a) What terminology is used to refer to such experimental set up?

(b) Work out the current flowing in the circuit.

7. Classify the following salts on the basis of solubility in water: Sodium carbonate, Lead nitrate, Silver chloride, Copper (Il) sulphate, Barium sulphate, Zinc chloride and Lead sulphate.

8. Table 2 shows the volume of soap solution needed to form lather with three samples of' water of equal volumes. Use the data from the table to answer the questions that follow:

Table 2

(a) Identify two things other than the volume of water that must be kept constant for such data to be meaningful.

(b) Identify which water sample has the highest hardness. Give a reason.

(ii) Give three causes of hardness of water.

9. Consider the following substances: milk, copper, soap, steel, chlorine and sugar.

(a) Identify the elements, compounds and mixtures from the list.

(b) Give four differences between the elements identified in 9(a).

10. (a) Explain the function of ceke and hot air in the extraction of iron from its ore.

(b) Account for the fact that aluminium is a vital element in our daily life. Give four points.

11. An unknown green sample was mixed with dilute HNO₃ and gave a blue solution and a gas which precipitated lime water. The resulting solution was evaporated to dryness and upon further heating black residues was formed together with a brown gas which relighted a glowing splint.

(a) Identify the green sample, blue solution, the black solid and the two gases.

(b) Give balanced chemical equation for the reaction between the green sample and nitric acid, and the equation for the formation of black residues.

12. (a) Distinguish alkanes from alkenes by giving three points.

(b) Why carbon has been given special attention in organic chemistry rather than other elements? Give four reasons.

SECTION C (15 Marks)

Answer one (1) question in this section.

13. Explain six effects of water pollution in Tanzania.

14. Describe six ways that can be adopted by the farmers to maintain soil fertility in Tanzania.