Question

The function of cryolite in the electrolytic reduction of alumina is: *

(a) As a catalyst

(b) To lower the temperature of the melt and enhance conductivity.

(c) To decrease the rate of oxidation of carbon at the anode

(d) None of the above

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Answer 1

Answer:

The melting point of alumina very high (2323 K). It is therefore, mixed with cryolite (Na3AIF6) which lowers its melting point to 1173 K. Moreover, cryolite also increase the electrical conductivity of alumina.

Answer 2

Answer:

Cryolite (Na3AlF6) has two roles in the electrolytic reduction of aluminium: 1. To decrease the melting point of the mixture from 2323 K to 1140 K