The pBlock Elements - Result Question 5
####6. Aluminium is extracted from alumina $(Al_2 O_3)$ by electrolysis of a molten mixture of: [2012]
(a) $Al_2 O_3+HF+NaAlF_4$
(b) $Al_2 O_3+CaF_2+NaAlF_4$
(c) $Al_2 O_3+Na_3 AlF_6+CaF_2$
(d) $Al_2 O_3+KF+Na_3 AlF_6$
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Solution:
- (c) Fused alumina $(Al_2 O_3)$ is a bad conductor of electricity. Therefore, cryolite $(Na_3 AlF_6)$ and fluorspar $(CaF_2)$ are added to purified alumina which not only make alumina a good conductor of electricity but also reduce the melting point of the mixture to around $1140 K$.
