In Hall - Heroult process, the following is used for reducing $\mathrm{Al}_{2} \mathrm{O}_{3}$ :-

(C) $\mathrm{Na}_{3} \mathrm{AlF}_{6}$

JEE Main · 2023 · 08 Apr 2023 · Shift 2 · General Principles and Processes of Isolation of Metals

In Hall - Heroult process, the following is used for reducing

Al_{2} O_{3}

(A)Graphite✓ Correct
(B)Magnesium
(C) $Na_{3} AlF_{6}$
(D) $CaF_{2}$

Answer: (A)

Solution

In the Hall\u2013H\u00e9roult process purified alumina is dissolved in molten cryolite and electrolysed. At the carbon anode the oxygen set free reacts with the graphite to form carbon monoxide and carbon dioxide, and this consumption of carbon is what brings about the reduction of alumina to aluminium. Cryolite and fluorspar only lower the fusion temperature and improve conductivity and are not reducing agents. The reducing agent is graphite.

JEE Main · 2023 · 08 Apr 2023 · Shift 2 · Single correct option

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