Question

The role of fluorspar ( CaF₂) which is added in small
quantities in the electrolytic reducation of alumina dissolved
in fused cryolite (Na₃AlF₆) is
(a) As a catalyst
(b) To make the fused mixture very conducting
(c) To increase the temperature of the melt.
(d) To decrease the rate of oxidation of carbon at the anode.

Answer 1

Answer:

b) to make the fused mixture very conducting

Explanation:

refer ncert metalurgy for detailed explanation...

Answer 2

The role of fluorspar ( CaF₂) which is added in small  quantities in the electrolytic reducation of alumina dissolved  in fused cryolite (Na₃AlF₆) is

(b) To make the fused mixture very conducting

We know, pure alumina (Al₂O₃) is a bad conductor of electricity. Difficulties like the vapourising of the metal is faced when the electrolysis of pure alumina is done at a temperature near to its melting point.

To escape this difficulty, instead of pure alumina, we use a mixture of alumina, flourspar (CaF₂) and cryolite (Na₃AlF₆) in the electrolytic reduction process and the fused mixture becomes conducting.