Q11 / 90 · JEE Main 2012 (12 May Online) · Chemistry

In the electrolysis of alumina to obtain aluminium metal, cryolite is added mainly to

  • Correct answer
    A
    lower the melting point of alumina
  • B
    dissolve alumina in molten cryolite
  • C
    remove the impurities of alumina
  • D
    increase the electrical conductivity

Solution

Fused alumina $\left(\mathrm{Al}_2 \mathrm{O}_3\right)$ is a bad conductor of electricity. Therefore, cryolite $\left(\mathrm{Na}_3 \mathrm{AlF}_6\right)$ and fluorspar $\left(\mathrm{CaF}_2\right)$ 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 $1140 \mathrm{~K}$.

Hence, the correct answer is option: 'A'.

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