Question

Cryolite is used in the electrolytic extraction of aluminium

• A. to obtain more aluminium
• B. to decompose bauxite
• C. to protect anodes
• D. as a reducing agent

Answer 1

Answer: (B)

Cryolite is used in the electrolytic extraction of aluminium to decompose bauxite.
$\underset{\text { cryolite }}{N a_{3} A l_{6}} \rightleftharpoons 3 N a F+A l F_{3} A l F_{3} \rightleftharpoons A l^{3+}+3 F^{-}$
At cathode $A l^{3+}+3 e^{-} \rightarrow A l(l)$
At anode $2 Al _{2} O _{3}+12 F ^{-} \rightarrow 4 AlF _{3}+6 O ^{2-}$
$C(s)+\underset{(\text { melt })}{O^{2-}} \rightarrow C O(g)+2 e^{-}$
$C(s)+\underset{(\text { melt })}{2 O^{2-}} \rightarrow C O_{2}(g)+4 e^{-}$