Question

5(c)(i) Name the chief ore of aluminium.
(ii) Why is the ore purified?
(iii) Name the electrode used in the electrolysis of bauxite to produce aluminium.
(iv) Give one reason why cryolite, NaAlF6, is added to the electrolyte.

Accepted Answer

(i) The chief ore of aluminium is bauxite.
(ii) The ore is purified because it contains impurities such as iron(III) oxide and trioxosilicates, which must be removed before electrolysis.
(iii) In the electrolysis of purified bauxite, the anode is made of graphite (carbon) while the cathode is iron.
(iv) Cryolite is added because it lowers the melting point of bauxite (alumina), reducing the energy cost of electrolysis; it also serves as a solvent for the alumina.

WAEC Chemistry 2019 Theory — Question 24

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