Waec Chemistry 2013 Past Questions and Answers

Question 51:

• WAEC 2013

(a)(i) Define the term standard electrode potential.
(ii) State three factors that affect the discharge of ions during electrolysis.
(iii) State two functions of a salt bridge in an electrochemical cell.
(b) Describe briefly what happens when a solution of copper (II) tetraoxosulphate (VI) is electrolyzed using copper electrodes.
c) Calculate the mass of copper deposited at the cathode when a current of 0.2A is passed through a solution of copper (II) tetraoxosulphate (VI) for 35 minutes using copper electrodes. [H = 1.00, O = 16.0, S = 32.0, Cu = 64.0, IF = 96,500C]
(d)(i) State three characteristics of a catalyst.
ii) Name one manufacturing process in which each of the following metals is used as catalyst: I. iron; II. nickel; Ill. platinum.
c-NA

Question 52:

• WAEC 2013

(a)(i) Define the term hygroscopic.
(ii) Give two difference: between a physical change and a chemical change.
(iii) Using the kinetic theory of gases, explain briefly the Charles' law.
(b)(i) Arrange the following compounds in order of increasing boiling points: CS\(_2\); CO\(_2\); NaH. Give reasons for your answer.
(ii) Write a balanced chemical equation to illustrate the reaction of chlorine gas with cold dilute sodium hydroxide.
(c) In a certain reaction, 15.0 g of impure magnesium sample reacted with excess hydrochloric acid liberating 8.6 dm\(^2\) of hydrogen gas at s.t.p.
(i) Write a balanced equation for the reaction.
(ii) Calculate the: I. mass of pure magnesium in the sample; I. percentage purity of the magnesium sample; III. number of ions produced in the reaction. [Mg = 24.0; volume at s.t.p. 22.4 dm\(^{-3}\), Avagadro's constant = 6.02 x 10\(^{23}\)mol\(^{-1}\)]

Question 53:

• WAEC 2013

(a)(i) Explain briefly the term chemical industry.
(ii) State three factors that should be considered in siting a chemical industry.
(b)(i) Describe briefly twin is extracted from its ore.
(ii) Give two uses of tin.
(c)(i) Name the constituents of cement.
(ii) How does mortar set?
(d)(i) Explain briefly the term pollution.
(ii) Give two examples of air pollutants.
(e) Consider the following reversible reaction which occurred at the temperature of 298K:
N\(_{2(g)}\) + 3H\(_{2(g)}\) \(\rightleftharpoons\) 2NH\(_{3(g)}\); \(\bigtriangleup\)H = —92.37kJ