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

Which among the following statement(s) is (are) true for the extraction of aluminium from bauxite?
  1. Hydrated Al2O3 precipitates, when CO2 is bubbled through a solution of sodium aluminate.
  2. Addition of Na3AlF6 lowers the melting point of alumina.
  3. CO2 is evolved at the anode during electrolysis.
  4. The cathode is a steel vessel with a lining of carbon.

Solution

(A) 2NaAlO2+3H2O+CO2⟶2Al(OH)3+Na2CO3

(B) In Hall-Heroult process Na3Al/F6 and CaF2 is mixed with Al2O3 to lower melting point and increase conductivity.

(C) Anode C(s)+2O2−(melt)→CO2(g)+4e−

(D) Steel cathode with carbon lining and graphite anode are used.

Asked in: JEE Advanced 2020 (Paper 2)

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