What is the role of graphite rod in the electrometallurgy of aluminium?

Options

A. It acts as anode
B. It acts as cathode
C. It acts as oxidising agent
D. Both (a) and (c)

Answer

A

Explanation

Graphite rods act as anode during the electrolytic reduction of alumina (Hall-Heroult process). At anode , `O_(2)` gas is produced which reacts with the carbon of anode (rods ) to produce `CO_(2)` gas , so these graphite rods are consumed slowly and need to be replaced from time to time.
`Al_(2)O_(3) iff 2Al^(3+) +3O^(2-)`
At cathode `Al^(3+) +3e^(-) to Al `
At anode `3O^(2-) to 3[O]+6e^(-) xx 2 `
`or 3[O]+3[O] to3O_(2)`
`C(s)+O_(2)(g) to CO_(2)(g)`