Question

Which of the following are added to concentrated alumina during the electrolytic reduction of alumina to aluminium by Hall-Heroult process?

• A. sodium chloride
• B. fluorite
• C. cryolite
• D. calcium carbonate

Answer 1

Answer: (B), (C)

cryolite

In Hall-Heroult process, cryolite ($N{a}_{3}Al{F}_6$) is added to concentrated alumina inorder to reduce the fusion temperature as well as to improve the conductivity of the melt. Apart from this, fluorspar ($Ca{F}_2$), also called fluorite, is also added to improve the conductivity.