Identify the components of the electrolyte other than pure alumina and the role played by each.

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Solution

Components present in electrolytic reduction of alumina are:
For the extraction of aluminium from alumina, cryolite and fluorspar are mixed in a $3 : 1$ ratio. Coke is also added.
The melting point of alumina is very high i.e., $2000^{°} C$ so cryolite $(N a_{3} A l F_{6})$ and fluorspar $(C a F_{2})$ are mixed and then the melting point becomes $900 - 950^{°} C$
Cryolite makes alumina a good conductor of electricity.
Fluorspar helps in increasing the mobility of the ions and acts as a solvent during the electrolysis process.
Coke does not allow the carbon rods to burn and reduces the heat loss.
$R e a c t i o n a t c a t h o d e : A l^{3} + 3 e^{-} \to A l R e a c t i o n a t a n o d e : 2 O^{2 -} \to O_{2} + 4 e^{-} C + O_{2} \to C O_{2}$

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