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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 $CO _2$.
$A,B,C$
$B,C,D$
$A,B$
$A,C$
Solution
$(A)$ Electrochemical extraction of Aluminum from bauxite done below $2500^{\circ} C$
$(B)$ $2 Na \left[ Al ( OH )_4\right]_{\text {aq. }}+2 CO _{2( g )} \rightarrow Al _2 O _3 \cdot 3 H _2 O _{( s )} \downarrow+2 NaHCO _{3( aq .)}$
The sodium aluminate present in solution is neutralised by passing $CO _2$ gas and hydrated $Al _2 O _3$ is precipitated.
$(C)$ $Al _2 O _{3( s )}+2 NaOH _{( aq .)}+3 H _2 O _{(\ell} \rightarrow 2 Na \left[ Al ( OH )_4\right]_{ aq }$.
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 $Na _3 AlF _6$
