Extraction of Metals - Result Question 20
####20. In the context of the Hall-Heroult process for the extraction of $Al$, which of the following statements is false?
(a) $CO$ and $CO _2$ are produced in this process
(2015 Main) (b) $Al _2 O _3$ is mixed with $CaF _2$ which lowers the melting point of the mixture and brings conductivity
(c) $Al^{3+}$ is reduced at the cathode to form $Al$
(d) $Na _3 AlF _6$ serves as the electrolyte
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Solution:
- (a) In Hall-Heroult process for extraction Al, carbon anode is oxidised to $CO$ and $CO _2$.
(b) When $Al _2 O _3$ is mixed with $CaF _2$, it lowers the melting point of the mixture and brings conductivity.
(c) $Al^{3+}$ is reduced at cathode to form $Al$.
(d) Here, $Al _2 O _3$ is an electrolyte, undergoing the redox process. $Na _3 AlF _6$ although is an electrolyte but serves as a solvent, not electrolyte.
