Which among the following statement(s) is (are) true for the extraction of aluminium from bauxite ?

Options

A. Hydrated `Al_2O_3` precipitates, when `CO_2` is bubbled through a solution of sodium aluminate
B. Addition of `Na_3AlF_6` lower the melting point of alumina.
C. `CO_2` is evolved at the anode during electrolysis.
D. The cathode is a steel vessel with a lining of carbon.

Answer

A, B, C, D

Explanation

(A) `2NaAl O_2 + 3H_2O + CO_2 to 2Al(OH)_(3) + Na_2CO_3`
(B) In Hall-Heroult process `Na_3AllF-6` and `CaF_2` is mixed with `Al_2O_3` to lower melting point & increase conductivity.
(C ) Anode `C(s ) + 2O^(2-) ("melt") to CO_2(g) + 4e^(-)`
(D) Steel cathode with carbon lining & graphite anode are used.