Which statement is incorrect regarding Hall-Heroult process for metallurgy of aluminium? 1. Use of…
Which statement is incorrect regarding Hall-Heroult process for metallurgy of aluminium?
1. Use of \(\mathrm{Na}_3 \mathrm{AlF}_6\) lowers the melting point of \(\mathrm{Al}_2 \mathrm{O}_3\)
2. Steel vessel with lining of carbon acts as cathode.
3. Graphite is used as anode.
4. Carbon dioxide gas is generated at cathode.
1
2
3
4
Solution
In Hall-Heroult process for extraction of aluminium (crude) from alumina \(\left(\mathrm{Al}_2 \mathrm{O}_3\right)\).
Statements (1), (2) and (3) are correct because cryolite \(\left(\mathrm{Na}_3 \mathrm{AlF}_6\right)\) is added to \(\mathrm{Al}_2 \mathrm{O}_3\) to lower, its melting point. Here, steel vessel with lining of carbon acts as cathode and graphite acts as anode, but statement (4) is incorrect because \(\mathrm{Al}\) gets deposited at cathode.