Question

In the context of the Hall-Heroult process for the extraction of Al, which of the following statements is false?

• A. $CO$ and $C{O}_2$ are produced in this process
• B. $A{l}_2{O}_3$ is mixed with $Ca{F}_2$, which lowers the melting point of the mixture and brings conductivity
• C. $A{l}^{3+}$ is reduced at the cathode to form $Al$
• D. $N{a}_{3}Al{F}_6$ serves as the electrolyte

Answer 1

The correct option is D

$N{a}_{3}Al{F}_6$ serves as the electrolyte

Since carbon electrodes are used, $CO$ and $C{O}_2$ are formed. In any cell - be it electrolytic or Galvanic - oxidation happens at the anode.
so clearly, the reduction of $A{l}^{3+}$ to $Al$ happens at the cathode. Also, concentrated $A{l}_2{O}_3$ is mixed with $Ca{F}_2$, which lowers the
melting point of the mixture and enhances conductivity.