Question

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

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

Answer 1

Answer: (A)

lower the melting point of alumina

Answer 2

Fused alumina $(Al_2O_3)$ is a bad conductor of electridty. Therefore, cryolite $(Na_3AlF_6)$ and fluorspar $(CaF_2)$ are added to piuified alumina which not only make alumina a good conductor of electricity but also reduce the melting point of the mixture to around 1140 K.