Describe the process of purification of impure copper using electroplating. [3 marks]

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Solution

In this process, the positive electrode (the anode) is made of the impure copper which is to be purified. The negative electrode (the cathode) is a bar of pure copper. The two electrodes are placed in a solution of copper sulphate. (1 mark)

Copper ions leave the anode and are attracted to the cathode, where they are deposited as copper atoms. $C u S O_{4} \to C u^{+ 2} (g o e s t o - v e t e r m i n a l) + S {O_{4}}_{4}^{- 2} (g o e s t o + v e t e r m i n a l)$
The pure copper cathode increases in size, while the anode dwindles away. The impurities left behind at the anode form a sludge beneath it. (1 mark)

(1 mark for diagram)

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The process of purification of an impure metal is like :
(a) electroplating a metal on the same type of metal
(b) electroplating a metal on another type of metal
(c) producing a chemical compound by electrolysis
(d) decomposing a chemical compound by electrolysis.

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