THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 

(For School Candidates Only)

TIME: 3 Hours Thursday, 7^th  October 2010 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. Calculators and cellular phones are not allowed in the examination room.

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

5. The following constants may be used:

Atomic masses: H = 1, O = 16, Na = 23, Mg = 24, C = 12

Cl = 35.5, K = 39, Pb = 207.

Avogadro’s number = 6.02 x 103 ²³.

GMV at s.t.p. = 22.4 dm .

1 Faraday = 96,500 coulombs.

Standard pressure = 760 mm Hg.

Standard temperature = 273 K.

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 among the given alternatives and write its letter beside the item number in the answer booklet provided.

(i) 1.4 g of potassium hydroxide is dissolved in water to form 250 cm³ of solution. What is the molarity of this solution?

1.  0.01 M
2.  0.1 M
3.  1.4 M
4.  5.6 M
5.  6.0 M

(ii) In the blast furnace carbon monoxide is prepared by passing carbon dioxide over a red­hot coke. Carbon dioxide is

1.  an accelerator
2.  an oxidizing agent
3.  a reducing agent
4.  a catalyst
5.  oxidized.

(iii) A catalyst can be described as a substance 

1. that alters the rate of reaction
2.  that slows down the rate of reaction
3.  used in every reaction so as to speed up rate of reaction
4.  that starts and speeds up the rate of reaction
5.  that terminates chemical reaction.

(iv) A covalent bond is formed when

1.  a metal combines with a non­metal
2.  potassium and oxygen combine
3.  ammonia is formed
4.  two metals combine
5.  atom looses an electron.

(v) A solvent can be obtained from a solution by

1.  evaporation followed by decantation
2.  filtration and condensation
3.  evaporation and filtration
4.  evaporation and condensation
5.  crystallization followed by sublimation.

(vi) Aqueous sugar solution is a poor conductor of electricity because

1.  water and sugar are covalent compounds
2.  water is a non­electrolyte
3.  sugar is a non­electrolyte
4.  sugar is covalent when in liquid form
5.  sugar dissolves completely in water.

(vii) The process of giving away water of crystallization to the atmosphere by a chemical substance is called

1.  efflorescence
2.  deliquescence
3.  hygroscopic
4.  sublimation
5.  vapourisation.

(viii) Copper can be separated from a mixture of zinc and copper by adding to the mixture

1.  concentrated H2SO ₄
2.  dilute H2SO 4
3.  aqueous solution of ZnSO4
4.  concentrated HNO₃
5.  a catalyst.

(ix) Among the factors that determine the ions to be discharged at electrodes when salt solutions are electrolysed are their

1.  non metallic nature
2.  relative concentrations in the solution
3.  relative ionic masses
4.  electronic configuration
5.  position in the periodic table.

(x) The mass of sodium hydroxide contained in 25 cm³ of 0.1 M NaOH is

1.  0.5 gm
2. B 2.85 gm
3.  250 gm
4.  0.2 gm
5.  25 gm