Question

a. Carbon monoxide cannot be used as reducing agent to extract aluminium from alumina. Why? 

b. The electrolytic cell for alumina is given below.

i. Al₂O₃ dissolved in molten cryolite is used as the electrolyte. What is the purpose of adding cryolite to alumina? 

ii. Anode is replaced from time to time while producing aluminium. Why? 

iii. Write the chemical equation of the reaction at the cathode.

Answer 1

a. Aluminium compounds are very stable,

b. i. The melting point of alumina is very high. Cryolite is added to alumina to reduce its melting point and increase its electrical conductivity, .

ii. Oxygen liberated at the anode reacts with carbon, forming CO

iii. Al³⁺ + 3e^- → Al