JEE Advanced · 2022 · 28 Aug 2022 · Paper 1 · General Principles and Processes of Isolation of Metals

The electrochemical extraction of aluminum from bauxite ore involves.

(A)the reaction of $Al_{2} O_{3}$ with coke (C) at a temperature $> 250 0^{\circ} C$ .
(B)the neutralization of aluminate solution by passing $CO_{2}$ gas to precipitate hydrated alumina $(Al_{2} O_{3} .3 H_{2} O)$ ✓ Correct
(C)the dissolution of $Al_{2} O_{3}$ in hot aqueous NaOH.✓ Correct
(D)the electrolysis of $Al_{2} O_{3}$ mixed with $Na_{3} AlF_{6}$ to give Al and $CO_{2}$ .✓ Correct

Answer: (B), (C), (D)

Solution

(A) Electrochemical extraction of aluminum from bauxite is done below 2500°C, not above it. Incorrect.

(B) The aluminate solution is neutralized by passing

CO_{2}

gas:

2 Na [Al (OH)_{4}]_{aq.} + 2 CO_{2 (g)} \to Al_{2} O_{3} \cdot 3 H_{2} O_{(s)} ↓ + 2 NaHCO_{3 (aq.)}

Correct.

(C) Bauxite is treated with hot concentrated NaOH solution:

Al_{2} O_{3 (s)} + 2 NaOH_{(aq.)} + 3 H_{2} O_{(l)} \to 2 Na [Al (OH)_{4}]_{aq}

Correct.

(D) In the Hall-Héroult process,

Al_{2} O_{3}

is mixed with

Na_{3} AlF_{6}

(cryolite) and electrolyzed to produce Al and

CO_{2}

. Correct.

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JEE Advanced · 2022 · 28 Aug 2022 · Paper 1 · General Principles and Processes of Isolation of Metals

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