Waec Chemistry 1991 Past Questions and Answers

Question 41:

• WAEC 1991

(a) Give the products of electrolysis of dilute copper (II) tetraoxosulphate(VI) solution using the following materials as electrodes:
(i) carbon rod;
(ii) copper rods

(b) For each of the process in (a) above;
(i) write the anodic half reaction;
(ii) state how electrolysis affects the pH of electrolyte

Question 42:

• WAEC 1991

(a) Give two reasons why fused alumina is mixed with cryolite in the electrolytic extraction of aluminium.
(b) Write an equation for the reaction of sodium hydroxide with bauxite.

Question 43:

• WAEC 1991

(a) Name the industrial process by which ethene is obtained from petroleum fractions
(b) Give the I. U. P.A.C name of the isomer whose structure is shown below.

(c) Illustrate with an equation, one reaction in which benzene behaves as:
(i) unsaturated hydrocarbon
(ii) a saturated hydrocarbon

Question 44:

• WAEC 1991

Give one oxide in each case which;
(a) can act as a reducing agent
(b) can be used as a refrigerant
(c) is the anhydride of a strong acid;
(d) is yellow when hot and white then hot and white when cold;
(f) is usad as a pigment in paints.

Question 45:

• WAEC 1991

Sketch a curve to show how the solubility of a gas varies with increasing temperature