In electrolysis of Al2O3 by Hall-Heroult process :

Chemistry General Principles and Processes of Isolation of Elements ( Not In Syllabus ) General Single Correct MCQ

Published by: CGP EDU Academic Team

Published on: August 12, 2026

Cryolite Na3[AlF6] lowers the melting point of Al2O3 and increases its electrical conductivity. and

Al is obtained at cathode and probably CO2 at anode are correct.

Both

None of the above is correct

Text Solution

Verified by Experts

The correct answer is:

Na3[AlF6] 3NaF + AlF3

NaF and AlF3 both are ionic compounds and so ionise to give ions. This increases the electrical conductivity and lowers the melting point of Al2O3 .

At cathode : Al3+ (melt) + 3e– Al.

At anode : C(s) + O2– (melt) CO (g) + 2e– ; C(s) + 2O2– (melt) CO2 (g) + 4e–.

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