When a metal atom becomes an ion : [Choose the correct answer from the choices A, B, C and D]

A : it loses electrons and is oxidized
B : it gains electrons and is reduced
C : it gains electrons and is oxidized
D : it loses electrons and is reduced

In the extraction of aluminium :

(i) Which soln. is used to react with bauxite as a first step in obtaining pure aluminium oxide.

(ii) The aluminium oxide for the electrolytic extraction of aluminium is obtained by heating aluminium hydroxide. Write the equation for this reaction.

(iii) Name the element which serves as the anode and cathode in the extraction of aluminium.

(iv) Write equation for the reaction at the cathode during the extraction of aluminium by electrolysis.

(v) Give the equation for the reaction at the anode when aluminium is purified by electrolysis.

The following is a sketch of an electrolytic cell used in the extraction of aluminium :

(i) What is the substance of which the electrodes A and B are made?

(ii) At which electrode (A or B) is the aluminium formed ?

(iii) What are the two aluminium compounds in the electrolyte C ?

(iv) Why is it necessary for electrode B to be continuously replaced ?

The metal oxide which can react with acid as well as alkali is :

1. Silver oxide
2. Copper [II] oxide
3. Aluminium oxide
4. Calcium oxide