JEE Main 12 Jan 2019 Morning Question 1
Question: In the Hall-Heroult process, aluminium is formed at the cathode. The cathode is made out of [JEE Main Online Paper Held On 12-Jan-2019 Morning]
Options:
A) Platinum
B) Pure aluminium
C) Copper
D) Carbon.
Show Answer
Answer:
Correct Answer: D
Solution:
In Hall-Heroult’s process, aluminium is formed at the cathode.
The cathode is made out of carbon. In this method, Al2 O3 is melted with crylite, Na3 [AlF6] and electrolyzed in a graphite lined steel tank,
which serves as the cathode. The anode is also made of graphite.
The cell runs continuously and at intervals, molten aluminium is drained from the bottom of the cell and more bauxite is added.
The electrolytic reaction is as follows:
$ \begin{aligned} \text{At cathode:} \\ \text{Al}^{3+} + 3\text{e}^- &\rightarrow \text{Al} \\ \text{At anode:} \\ \text{C} (s) + \text{O}_2^- (\text{melt}) &\rightarrow \text{CO} (g) + 2\text{e}^- \ \text{C}(s) + 2\text{O}_2^- (\text{melt}) &\rightarrow \text{CO}_2 (g) + 4\text{e}^- \end{aligned} $
