Question

In the extraction of Aluminium by electrolysis:
i) Given the composition of electrolyte used
ii) Overall cell reaction
iii) Role of cryolite

Answer 1

In the extraction of Aluminium by electrolysis:
i) The composition of electrolyte is alumina $(2-8)$%, synthetic cryolite $N{a}_{3}Al{F}_6(80-85)$ %, $Al{F}_3(5-7)$% and fluorspar $Ca{F}_2(5-7)$%
ii) Overall cell reaction
$2A{l}_2{O}_3+6F_2\to 4Al{F}_3+3O_2$
$2Al{F}_3\to 2Al+3F_2$
iii) Role of cryolite:

Cryolite (and fluorspar) makes alumina good conductor of electricity and lowers the fusion temperature to around 1140 K.