JEE Main2012ChemistryGeneral Principles and Processes of Isolation of MetalsActual

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

Options

Alower the melting point of alumina
Bdissolve alumina in molten cryolite
Cremove the impurities of alumina
Dincrease the electrical conductivity

Correct answer

A. lower the melting point of alumina

Step-by-step solution

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 .

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