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.
This paper consists of section A, B and C
Answer all questions in this paper
Calculators and cellular phones are not allowed in examination room.
Write your Examination Number on every page of your answer booklet(s)
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?
Water molecules have stopped changing into ions.
Water molecules have all changed into ions
Concentrations of water molecules and ions are equal
Concentrations of water molecules and ions are constant
Water molecules are moving slow.
(ii) The property of metal to be drawn into wires is called?
Conductivity
Malleability
Ductility
Decorating
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.
30g.
56g.
0.54g.
28g.
0.52g.
(iv) What will happen when zinc is placed in aqueous copper (II) sulphate?
Copper atoms are oxidized
Zinc atoms are oxidized
Copper ions are oxidized
Zinc ions are oxidized
Sulphur atoms are oxidized.
(v) Which of the following pair of gas can be prepared in the laboratory and collected over water?
Oxygen and Ammonia
Hydrogen and Hydrochloric acid
Hydrogen and Ammonia
Oxygen and Hydrogen chloride
(vi) Two substances are allotropes of carbon if
Both reduce heated iron (II) oxide to iron
Have different crystalline structure
Have equal masses
Have equal shape
Have the same arrangement of atoms
(vii) The apparatus suitable for measuring specific volumes of liquids is called?
Burette
Volmetric flask
Pipette
Measuring cylinder
Graduated beaker
(viii) The reaction represents which among the following reactions.
Synthesis
Precipitation
Neutralization
Displacement
Decomposition
(ix) The occurrence of two or more compounds with the same molecular formula but different molecular structures is known as.
Amphoterism
Isomerism
Allotropy
Polymorphism
Isotopy
(x) Which of the following sets of symbols represent isotopes of a single element?
16 8 X, 17 8 X, 18 8 X
16 8 Z, 17 8 Z, 18 8 X
16 7 P, 16 8 P, 16 9 P
16 7 K, 17 8 K, 18 9 K
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.
LIST A | LIST B |
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SECTION B:
3. (a) Give the meaning of the following terms.
Soil Ph
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)
View Ans4. (a) Differentiate dilute hydrochloric acid from dilute sulphuric acid.
View Ans(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.
Why does Steven think that John’s conclusion is wrong?
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.
Water sample | Volume of soap solution required (cm 3 ) before boiling | Volume of soap solution required (cm 3 ) after boiling |
A | 5.0 | 5.0 |
B | 1.0 | 1.0 |
C | 11.0 | 8.0 |
D | 9.0 | 1.0 |
Which sample probably contains temporary hardness of water only?
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:
But-2-ene.
Pent-2-yne
1,2-dichloroethane
2,4-dimethylhexane.
(b) Briefly explain what will be observed when silver nitrate solution is added to aqueous solution of sodium chloride.
View Ans7. (a) Determine the empirical formula of a substance that has the following composition by mass; 49.5% oxygen.
View Ans(b) Give one reason why Alluminium is chosen to make each of the following items:
Cooking foil
Overhead electric cables
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.
View Ans(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.
View Ans9. (a) Name two elements which are expected to show similar chemical reaction with magnesium. What is the basis for your choice?
View Ans(b) State the main raw material and the process involved in the manufacture of the following products.
Wood charcoal
Coke
Lampblack.
10. (a) Give two chemical tests of water and the expected result to be observed.
View Ans(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?
Neutral solution
Strong acid
Strong alkali
Weak acid.
11. (a) State the meaning of the following and give one example in each case.
Amphotenic oxide
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.
Solution | Aluminium | Barium | Lithium | Magnesium |
Aluminium nitrate | X | | | |
Barium nitrate | | x | | x |
Lithium nitrate | X | | x | |
Magnesium nitrate | x | | | x |
Where: = reaction observed and X = no reaction.
Use the most results given to arrange the metals in order of reactivity starting with the most reactive metal.
Use the reactivity series in 11 (b) (i) to complete Table 2.
SECTION C:
12. Explain five methods to prevent terrestrial pollution.
View Ans13. 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;
The number of moles of copper that were formed and the number of moles of M that were used in the reaction.
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.
View Ans