JEE Advance - Chemistry (2022 - Paper 1 Online - No. 11)
The electrochemical extraction of aluminum from bauxite ore involves
the reaction of $\mathrm{Al}_{2} \mathrm{O}_{3}$ with coke $(\mathrm{C})$ at a temperature $>2500^{\circ} \mathrm{C}$.
the neutralization of aluminate solution by passing $\mathrm{CO}_{2}$ gas to precipitate hydrated alumina $\left(\mathrm{Al}_{2} \mathrm{O}_{3} \cdot 3 \mathrm{H}_{2} \mathrm{O}\right)$.
the dissolution of $\mathrm{Al}_{2} \mathrm{O}_{3}$ in hot aqueous $\mathrm{NaOH}$.
the electrolysis of $\mathrm{Al}_{2} \mathrm{O}_{3}$ mixed with $\mathrm{Na}_{3} \mathrm{AlF}_{6}$ to give $\mathrm{Al}$ and $\mathrm{CO}_{2}$.
Explanation
(A) The reduction of Al2O3 with coke (C) at a temperature > 2500$$^\circ$$C is not carried out due to the formation of carbides.
(B) It is correct as neutralisation of aluminate solution is done by passing CO2 gas to precipitate hydrated alumina.
(C) Reaction of powdered one is carried out with hot concentrated NaOH at 473 K - 523 K and 35 - 36 bar pressure.
(D) Electrolysis of Al2O3 is done mixed with Na3AlF6 to produce Al and CO2. It is a correct statement.
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