JEE Advanced 2022 · Paper 1 · Chemistry Q11

ChemistryMultiple correct+4 / -2Question 47 of 54

The electrochemical extraction of aluminum from bauxite ore involves

the reaction of

\ce{Al2O3}

with coke (C) at a temperature > 2500 °C.

the neutralization of aluminate solution by passing

\ce{CO2}

gas to precipitate hydrated alumina (

\ce{Al2O3.3H2O}

the dissolution of

\ce{Al2O3}

in hot aqueous NaOH.

the electrolysis of

\ce{Al2O3}

mixed with

\ce{Na3AlF6}

to give Al and

\ce{CO2}

Answer and worked solution

Official answer: B, C, D

Bayer process (purifying the bauxite):

(C) Alumina dissolves in hot NaOH as aluminate.
(B) Passing $\ce{CO2}$ precipitates $\ce{Al2O3.3H2O}$ , which is then calcined.

Hall-Héroult process:

(D) Alumina dissolved in molten cryolite, $\ce{Na3AlF6}$ , is electrolysed. The carbon anodes are oxidised to $\ce{CO2}$ (and CO).

(A) False. Aluminium is not obtained by carbon reduction; $\ce{Al2O3}$ is too stable for that.

JEE Advanced 2022 · Paper 1, Chemistry question 11