Question

Which statement is incorrect regarding Hall-Heroult process for metallurgy of aluminum?
1. Use of $N{a}_{3}Al{F}_6$ lowers the melting point of $A{l}_2{O}_3$
2. Steel vessel with lining of carbon acts as cathode
3. Graphite is used as anode
4. Carbon dioxide gas is generated at cathode

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (D)

In Hall-Heroult process for extraction of aluminium (crude) from alumina $\left(A{l}_2{O}_3\right)$. Statements $(1),(2)$ and $(3)$ are correct because cryolite $\left(N{a}_{3}Al{F}_6\right)$ is added to $A{l}_2{O}_3$ 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 $Al$ gets deposited at cathode.