Question

In the metallurgy of aluminium,
A. `Al^(3+)` is oxidation to Al (s).
B. graphide anode is oxidation to carbon monoxide and carbon dioxide.
C. oxidation state of oxygen changes in the reaction at anode.
D. oxidation state of oxygen in the overall reaction involved in the process.

Answer 1

Correct Answer - B
(b) In the metallurgy of aluminium , electrolysis is performed in a steel vessel with lining of carbon acts as cathode and graphite acts as anode. During this process graphite Chemical reaction to CO and `CO_(2)` .
`2Al_(2)O_(3) + 3C to 4Al + 3CO_(2)`
This process is known as Hall-Herolt process. The electrolytc reactions are
At cathode `Al^(3+)` (melt) `+3e^(-) to Al(l)`
At anode `C(s) + O^(2-)("melt") to CO(g) +2e^(-)`
`" "C(s)+2O^(2-) ("melt") to CO_(2)(g) +4e^(-)`