In the metallurgy of aluminium_________

Options

A. `A1^(3+)`is oxidised to `A1(s)`.
B. graphite anode is oxidised to carbon monoxide and carbon dioxide.
C. oxidation state of oxygen changes in the reaction at anode.
D. oxidation state of oxygen changes in the overall reaction involved in the process.

Answer

B

Explanation

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 graphic anode is oxidised to `CO`and`CO_(2)`
Chemical reaction occurring in this process is as follows
`A1_(2)O_(3) +3Crarr 4A1 +3O`
This process is known as Hall-Heroult process. the electorlytic reactions are
At cathod: `A1^(3+)("melt") +3e^(-)rarr A1(l)`
At anode: `C(s) +O^(2-)("metl")rarr Co(g) +2e^(-)`
`C(s) +2O^(2-)("melt") rarr CO_(2)(g)+4e^(-)`