Question

During extraction of aluminium from bauxite,

• A. the concentration of ore is done by gravity separation method
• B. molten mixture of aluminium oxide, cryolite and fluorspar is electrolysed
• C. impure aluminium is refined by liquation
• D. molten aluminium is obtained at cathode while fluorine is liberated at anode.

Answer 1

The Correct Option is B

Purified ${Al_2O_3}$ is mixed with ${Na_3AlF_6}$ and ${CaF_2}$ to improve conductivity of ${Al_2O_3}$ and to lower the melting point of the mixture.
${Al_2O_3 ->[Electrolysis] 2Al^{3+} + 3O^{2-}}$
At cathode : ${Al^{3+} + 3e^- ? Al}$
At anode : ${C + O^{2-} ? CO + 2e^-}$
${ C + 2O^{2-} \rightarrow CO_2 + 4e^-}$