Chemistry · Metallurgy

JEE Advanced 2022 — Paper 1 — Question 43

The electrochemical extraction of aluminum from bauxite ore involves

Option A:
the reaction of $\mathrm{Al}_{2} \mathrm{O}_{3}$ with coke (C) at a temperature $>2500^{\circ} \mathrm{C}$ .
Option B:
the neutralization of aluminate solution by passing $\mathrm{CO}_{2}$ gas to precipitate hydrated alumina $\left(\mathrm{Al}_{2} \mathrm{O}_{3} \cdot 3 \mathrm{H}_{2} \mathrm{O}\right)$ .
Correct
Option C:
the dissolution of $\mathrm{Al}_{2} \mathrm{O}_{3}$ in hot aqueous NaOH .
Correct
Option D:
the electrolysis of $\mathrm{Al}_{2} \mathrm{O}_{3}$ mixed with $\mathrm{Na}_{3} \mathrm{AlF}_{6}$ to give Al and $\mathrm{CO}_{2}$ .
Correct

Answer: B, C, D

Step-by-step solution

$2 \mathrm{NaAlO}_{2}+\mathrm{CO}_{2}+3 \mathrm{H}_{2} \mathrm{O} \longrightarrow 2 \mathrm{Al}(\mathrm{OH})_{3} \downarrow+\mathrm{Na}_{2} \mathrm{CO}_{3}$

$2 \mathrm{Al}(\mathrm{OH})_{3} \xrightarrow{\Delta} \mathrm{Al}_{2} \mathrm{O}_{3}+3 \mathrm{H}_{2} \mathrm{O}$

$\rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+2 \mathrm{NaOH} \longrightarrow 2 \mathrm{NaAlO}_{2}+\mathrm{H}_{2} \mathrm{O}$ $\rightarrow$ During electrolysis of alumina, cryolite

$\left(\mathrm{Na}_{3} \mathrm{AlF}_{6}\right)$ and fluorspar $\left(\mathrm{CaF}_{2}\right)$

are added to decrease the melting point of alumina. $\rightarrow \mathrm{Al}$ metal is obtained at cathode while

$\mathrm{CO}_{2}$ releases at anode.

Answer key and solution verified before publishing.

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Exam: JEE Advanced 2022
Paper: Paper 1
Subject: Chemistry
Chapter: Metallurgy
Topic: Individual Extractions of Different Metals + Misc

The treatment of galena with HNO 3 produces a gas that is

Answer: B, C, D

Step-by-step solution

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