Question

In the electrolysis of alumina, cryolite is added to
A. Lower the melting point of alumina
B. Increase the electrical conductivity
C. Minimise the anode effect
D. Remove the impurities from alumina

Answer 1

Correct Answer - A::B
The electrolysis of pure alumina faces some difficulties. Pure alumina is a bad conductor is of electricity. This fusion temperature of pure alumina is about `2000^@C`, and at this temperature, when the electrolysis is carried out on the fused mass, the metal formed vaporises as the boiling point aluminium is `1800^@ C`. These difficulties are overcome by using a mixture containing alumina, cryolite `(Na_(3)AlF_(6))`, and fluorpar `(CaF_(2))`.