Electrolytic reduction of alumina to aluminum by the Hall-Heroult process is carried out

Options

A. In the presence of `NaCl`
B. In the presence of fluorite
C. In the presence of cryolite, which forms a melt with lower melting temperature
D. In the presence of cryolite, which forms a melt with higher melting temperature

Answer

C

Explanation

The electrolysis of pure alumina faces some difficulties, Pure alumina is a bad conductor of electricity. The 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 fluorspar `(CaF_(2))`.