Question

The role of fluorspar, which is added in small quantities in the electrolysis reduction of alumina dissolved in fused cryolite, is:

• A. as a catalyst
• B. to make fused mixture conducting
• C. to lower the melting temperature of the mixture
• D. to decrease the rate of oxidation of carbon at anode

Answer 1

Answer: (B), (C)

to make fused mixture conducting
to lower the melting temperature of the mixture

The role of fluorspar $Ca{F}_2$, which is added in small quantities in the electrolytic reduction of alumina $(A{l}_2{O}_3)$ dissolved in fused cryolite $N{a}_{3}Al{F}_6$, is to make the fused mixture a good conductor of electricity and to lower the melting temperature of the mixture to around 1140 K.