In the commercial electrochemical process for aluminium extraction, the electrolyte used is

Options

A. `Al(OH)_(3)` in `NaOH` solution
B. An aqueous solution of `Al_(2)(SO_(4))_(3)`
C. A molten mixture of `Al_(2)O_(3)` and `Na_(3)AlF_(6)`
D. A molten mixture of `AlO(OH)` and `Al(OH)_(3)`

Answer

C

Explanation

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 of aluminium is `1800^@C`. These difficulties are overcome by using a mixture containing alumina, cryolite `(Na_(3)AlF_(6))`, and `(CaF_(2))`.