THE UNITED REPUBLIC OF TANZANIA

NATIONAL EXAMINATIONS COUNCIL CERTIFICATE OF SECONDARY EDUCATION EXAMINATION.

032/1 CHEMISTRY 1

(For Both school and Private Candidates)

Time: 3Hours Friday, 04  ^th   November 2016 a.m

Instructions.

1. This paper consists of section A, B and C

2. Answer all questions in this paper

3. Calculators and cellular phones are not  allowed in examination room.

4. Write your Examination Number on every page of your answer booklet(s)

5. The following constants may be used.

Atomic masses: C = 12, O = 16, Mg = 24, Al = 26, S = 32,

Cl = 35.5, Mn = 55, Fe = 56, Cu = 63.5,

Avogadro ’s number = 6.02 _x_  10  ²³  ,

GMV at s.t.p = 22.4dm  ³ 

1Faraday = 96,500 coulombs

Standard pressure = 760mm Hg.

Standard temperature = 273 K,

1 litre = 1dm  ³  = 1000cm  ³ 

SECTION A:

1. 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 of the following is True about the following equilibrium?

1. Water molecules have stopped changing into ions.

2. Water molecules have all changed into ions

3. Concentrations of water molecules and ions are equal

4. Concentrations of water molecules and ions are constant

5. Water molecules are moving slow.

(ii) The property of metal to be drawn into wires is called?

1. Conductivity

2. Malleability

3. Ductility

4. Decorating

5. Expansion.

(iii) If a steady current of 2 amperes was passed through an aqueous solution of iron (II) sulphate for 15 minutes, the mass of iron deposited at the cathode will be.

1. 30g.

2. 56g.

3. 0.54g.

4. 28g.

5. 0.52g.

(iv) What will happen when zinc is placed in aqueous copper (II) sulphate?

1. Copper atoms are oxidized

2. Zinc atoms are oxidized

3. Copper ions are oxidized

4. Zinc ions are oxidized

5. Sulphur atoms are oxidized.

(v) Which of the following pair of gas can be prepared in the laboratory and collected over water?

1. Oxygen and Ammonia

2. Hydrogen and Hydrochloric acid

3. Hydrogen and Ammonia

4. Oxygen and Hydrogen chloride

(vi) Two substances are allotropes of carbon if

1. Both reduce heated iron (II) oxide to iron

2. Have different crystalline structure

3. Have equal masses

4. Have equal shape

5. Have the same arrangement of atoms

(vii) The apparatus suitable for measuring specific volumes of liquids is called?

1. Burette

2. Volmetric flask

3. Pipette

4. Measuring cylinder

5. Graduated beaker

(viii) The reaction  represents which among the following reactions.

1. Synthesis

2. Precipitation

3. Neutralization

4. Displacement

5. Decomposition

(ix) The occurrence of two or more compounds with the same molecular formula but different molecular structures is known as.

1. Amphoterism

2. Isomerism

3. Allotropy

4. Polymorphism

5. Isotopy

(x) Which of the following sets of symbols represent isotopes of a single element?

1.  ¹⁶  ₈  X,  ¹⁷  ₈  X,  ¹⁸  ₈  X

2.  ¹⁶  ₈  Z,  ¹⁷  ₈  Z,  ¹⁸  ₈  X

3.  ¹⁶  ₇  P,  ¹⁶  ₈  P,  ¹⁶  ₉  P

4.  ¹⁶  ₇  K,  ¹⁷  ₈  K,  ¹⁸  ₉  K

5.  ¹⁶  ₇  U,  ¹⁶  ₈  U,  ¹⁸  ₁₀  U

2. Match the items in List A with the responses in List B by writing the letter of the correct response beside the item number in the answer booklet provide.

 SECTION B: 

3. (a) Give the meaning of the following terms.

1. Soil Ph

2. Liming.

(b) (i) Explain why sulphur and its compounds are removed from fuels before they are burned.

(ii) Describe how sulphur dioxide is changed into sulphur trioxide. Give the reaction conditions and the equation(s)

4. (a) Differentiate dilute hydrochloric acid from dilute sulphuric acid.

(b) John measured the volume of gas produced when 5 g of two chemicals X and Y were added separately to hydrogen peroxide under identical conditions. His results for this experiment are represented on the graph below.

John claimed that Y is a better catalyst than X. His partner Steven did not agree.

1. Why does Steven think that John’s conclusion is wrong?

2. After the experiment, Steven recovered 5 g of X and 1 g 1 of Y from the two experiments. He claimed that John was wrong. Does Steven’s claim true? Give a reason.

5. (a) Give the name of the type of reaction represented by each of the following chemical equations.

(b) 25cm  ³  samples of water A, B, C and D were tested with soap solution. The volume of soap solution required to produce a lather that lasted for a minute was recorded. Fresh samples of each were boiled and tested again with soap solution. The results are shown in Table 1.

Table 1.

1. Which sample probably contains temporary hardness of water only?

2. Which sample probably contains both permanent and temporary hardness of water? Give a reason for your answer.
   
   

6. (a) Write the structural formula for the following compounds:

1. But-2-ene.

2. Pent-2-yne

3. 1,2-dichloroethane

4. 2,4-dimethylhexane.

(b) Briefly explain what will be observed when silver nitrate solution is added to aqueous solution of sodium chloride.

7. (a) Determine the empirical formula of a substance that has the following composition by mass; 49.5% oxygen.

(b) Give one reason why Alluminium is chosen to make each of the following items:

1. Cooking foil

2. Overhead electric cables

3. Window frames

8. (a) Identify and state the environmental problem caused by the gas which is released from the blast furnace in the extraction of iron from its oxide.

(b) (i) Draw a labeled diagram of a simple electrolytic cell which show how copper is purified.

(ii) Write balanced ionic equations to show the electrode reactions which occur when copper is purified.

9. (a) Name two elements which are expected to show similar chemical reaction with magnesium. What is the basis for your choice?

(b) State the main raw material and the process involved in the manufacture of the following products.

1. Wood charcoal

2. Coke

3. Lampblack.

10. (a) Give two chemical tests of water and the expected result to be observed.

(b) A student tested five solutions M, N, O, P and Q with a universal indicator solution to find their pH values. The following results were obtained.

Which of the above solutions was?

1. Neutral solution

2. Strong acid

3. Strong alkali

4. Weak acid.

11. (a) State the meaning of the following and give one example in each case.

1. Amphotenic oxide

2. Acidic oxide.

(b) A student investigated different reactivity of a set of metals by placing pieces of each metal in metal nitrate solution. Table 2 shows some of the results.

Table: 2.

Where: _{ } = reaction observed and X = no reaction.

1. Use the most results given to arrange the metals in order of reactivity starting with the most reactive metal.

2. Use the reactivity series in 11 (b) (i) to complete Table 2.

 SECTION C: 

12. Explain five methods to prevent terrestrial pollution.

13. 0.48g of a metal, M was placed in a test tube and hot copper (II) sulphate solution was added to it and stirred until the reaction stopped. The metal (M) displaced copper from copper (II) sulphate solution. Copper was filtered, washed with water, dried at 100⁰ C _ and the mass found to be 1.27g. Given that, the balanced chemical reaction that occurred is M _(s)  + CuSO  _4(aq)  MSO  _4(aq)  + Cu  _(s) 

(a) Calculate;

1. The number of moles of copper that were formed and the number of moles of M that were used in the reaction.

2. The relative atomic mass of M and hence identify metal M.

(b) State the appearance of the metal formed (Cu).

(c) With ionic equations, explain why the reaction can be considered to involve both oxidation and reduction.