Question

The electrochemical extraction of aluminum from bauxite ore involves.

• A. the reaction of $Al _2 O _3$ with coke (C) at a temperature $>2500^{\circ} C$.
• B. the neutralization of aluminate solution by passing $CO _2$ gas to precipitate hydrated alumina $\left( Al _2 O _3 .3 H _2 O \right)$
• C. the dissolution of $Al _2 O _3$ in hot aqueous $NaOH$.
• D. the electrolysis of $Al _2 O _3$ mixed with $Na _3 AlF _6$ to give $Al$ and $CO _2$.

Answer 1

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

(A) Electrochemical extraction of Aluminum from bauxite done below $2500^{\circ} C$
(B) $2 Na \left[ Al ( OH )_4\right]_{ aq .}+2 CO _{2( g )} \rightarrow Al _2 O _3 .3 H _2 O _{\text {(s) }} \downarrow+2 NaHCO _{3( aq .)}$
The sodium aluminate present in solution is neutralised by passing $CO _2$ gas and hydrated $Al _2 O _3$ is precipitated.
(C) $Al _2 O _{3( s )}+2 NaOH _{\text {(aq.) }}+3 H _2 O _{(l)} \rightarrow 2 Na \left[ Al ( OH )_4\right]_{\text {aq. }}$
Concentration of bauxite is carried out by heating the powdered ore with hot concentrated solution of $NaOH$
(D) In metallurgy of aluminum, $Al _2 O _3$ is mixed with $Na _3 AlF _6$