During the electrolysis of Al 2 O 3 by Hall-Heroult process…

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

Published on: August 13, 2026

During the electrolysis of Al 2 O 3 by Hall-Heroult process. Al 2 O 3 is mixed with cryolite and is electrolysed using graphite lined steel tanks which serve as cathode. The anodes are also made of graphite. The cell runs continously and at various intervals Al is removed from bottom of the cell. Aluminium obtained here has 99% purity.

(i) At anode the reaction taking place is -

2O 2– ⎯→ O 2 + 4e – C + O 2 ⎯→ CO 2 Bauxite – Al 2 O 3 .2H 2 O Al(CN) 3 is precipitated

F – ⎯→ F 2 C + 2F 2 ⎯→ CF 4 Cryolite – Na 3 AlF 6 Al(OH) 3 is precipitated

[AlF 6 ] 3– ⎯→ 3F 2 + Al + 6e – Kaolin – Al 2 O 3 .2SiO 2 .2H 2 O K 3 [Al(CN) 6 ] is formed

All of these (ii) Which of the following ores of aluminium is not correctly matched ? Quartz – KAlSi 2 O 8 (iii) When aqueous solution of potassium cyanide is added to Al 2 (SO 4 ) 3 then - Al 2 C 3 is formed

Text Solution

Verified by Experts

The correct answer is:

Ans.

(i)

Sol.

(ii)

Sol. Quartz is SiO 2

(iii)

Sol. KCN solution is alkaline, hence Al(OH) 3 is precipitated and formation constant of K 3 [Al(CN) 6 ] not higher.

Previous Question Next Question

Prepare Smarter with CGP Edu

Get practice questions, solutions, and test series in one place.

Write a Review

Share your experience with this question and solution.

Commentary

Send your comment, doubt, correction, or feedback to admin.

Student Reviews

What students say about this solution

No reviews yet. Be the first to write a review.

Share this question

Text Solution

Prepare Smarter with CGP Edu

Write a Review

Commentary

Student Reviews

Similar Questions