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In Hall's process for the preparation of...

In Hall's process for the preparation of `Al,` graphite anode has a long life.

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The correct Answer is:
F
Molten `Al_(2)O_(3)+Na_(3)AlF_(6)(` Cryolite `)+CaF_(2)(` Fluorspar`)+AlF_(3)` is used.
The electrolysis of this mixture is carried out using carbon `(` graphit `)` electrodes. The `O_(2)` liberated at the anode reacts with the graphite anode producing `CO` and `O_(2)`. Thus, a graphit anode needs to be replaced periodically.
Thus, graphite anodes do not have long life.
The overall reactions are as follows`:`
Cathode `:Al^(+3)(melt)+3e^(-) rarr Al^(l)`
Anode `:C(s)+O^(2-)(melt) rarr CO(g)+2e^(-)`
`C(s)+2O^(2-)(melt) rarr CO_(2)(g)+4e^(-)`
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