Chemistry Past Questions and Answers

A colourless and odourless gas X burns in oxygen with a pale blue flame.
(a) Suggest two gases which X could be.
(b) Give one chemical test that could be used to confirm which of the two gases X is.

Methane is obtained when a powdered mixture of anhydrous sodium ethanoate and soda-lime is heated in a hard glass test tube.
(a) Write an equation for the reaction.
b) Explain briefly why soda-lime is preferred to sodium hydroxide for the preparation.

(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

(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.

(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