(a) If a steel spoon were to be plated with silver, state what would be suitable for use as the;
(i) anode. (ii) cathode; (iii) electrolyte
(b)(i) Write an equation for one of the reactions involved in the purification of bauxite.
(ii) Give the reason why the carbon anodes are changed at intervals during the electrolysis of pure alumina solution in molten cryolite.
Explanation
(a) To electroplate a steel spoon with silver we use (i) Silver rod as anode
(ii) The steel spoon as cathode
(iii) Solution of silver salt e.g. AgNO\(_3\), silver cyanide\(_{(aq)}\) as electrolyte or any other Ag\(^{+}\) solution.
(b) Equation for the reactions in the extraction of aluminium.
(i) 2Al(OH)\(_3\) —> Al\(_2\)O\(_3\) + 3H\(_2\)O. Al\(_2\)O\(_3\) + 2NaOH + 2H\(_{2}\)O -> 2NaAl(OH)\(_4\) NaAl(OH)4 -› Al(OH)\(_3\) + NaOH
(ii) Why anodes are changed at intervals: The oxygen given off burns away the anode as carbon (IV) oxide.