Question

In the electrolysis of alumina, cryolite is added to

• A. lower the melting point of alumina
• B. increase the electrical conductivity
• C. minimise the anode effect
• D. remove impurities from alumina

Answer 1

Answer: (B)

increase the electrical conductivity

Answer 2

Alumina $(Al_2O_3)$ has very high melting point and it is poor conductor of electricity. Both these factors posses difficulty in electrolysis of molten alumina.
Cryolite. $Na_3AIF_6$, when mixed with alumina, lowers melting point as well as improve electrical conductivity, hence helps in electrolysis of $Al_2O_3$.