JEE Advanced2020ChemistryGeneral Principles and Processes of Isolation of MetalsActual
Which among the following statement(s) is (are) true for the extraction of aluminium from bauxite?
Options
- AHydrated Al 2 O 3 precipitates, when CO 2 is bubbled through a solution of sodium aluminate.
- BAddition of Na 3 AlF 6 lowers the melting point of alumina.
- CCO 2 is evolved at the anode during electrolysis.
- DThe cathode is a steel vessel with a lining of carbon.
Correct answer
A. Hydrated Al 2 O 3 precipitates, when CO 2 is bubbled through a solution of sodium aluminate.
Step-by-step solution
(A) 2 NaAlO 2 + 3 H 2 O + CO 2 ⟶ 2 Al ( OH ) 3 + Na 2 CO 3 (B) In Hall-Heroult process Na 3 Al / F 6 and CaF 2 is mixed with Al 2 O 3 to lower melting point and increase conductivity. (C) Anode  C ( s ) + 2 O 2 − ( melt ) → CO 2 ( g ) + 4 e − (D) Steel cathode with carbon lining and graphite anode are used.