a) Write the equation of the chemical reaction taking place at anode and cathode electrolytic refining of aluminium.
b) Carbon monoxide cannot be used as reducing agent to extract aluminium from alumina. Why?
c) Anode replaced from time to time while producing aluminium. Why?

Explanation

a) Anode : `2O^2- rarr O_2 + 4e^-`
Cathode : `Al^3+ + 3e^- rarr Al
b) Aluminium compounds are more stable. Thus electricity in used as reducing agent.
c. Oxygen liberated at the anode oxidises the carbon rods, carbon rods are to replaced often to form `CO_2`
As a result of this anode is demaged hence it is replaced often.