Extraction of aluminium can be understood by :

Electrolytric reduction of `Al_(2) O_(3)` :
Electrolysis : `Al_(2) O_(3) + Cryolite + CaF_(2)`
Cathode : Carbon inside the `Fe` container
Anode : Graphite rods.
The motion electrolytes contain `Na^(oplus),Al^(3+)` and `Ca^(2+)` but only `Al` gets deposited at cathode because,

Options

A. Standard reduction potential of `Al` is more than those of `Na & Ca`
B. Standard oxidation potential of `Al` is more than those of `Na & Ca`
C. Graphite reacts only with `Al^(3+)` and not with `Na^(+) & Ca^(2+)`
D. Discharge potential of `Al^(3+)` is higher than `Na^(+) & Ca^(2+)`

Answer

A