Question

For the electro-refining of copper. (i) What is the cathode made up of? (ii) Write the reaction that takes place at the anode.

Answer 1

Hint: (i)During the electrolytic refining of copper, both electrodes are made from copper metal. One electrode is pure copper metal and the other electrode is impure copper metal.
(ii) We are very well aware that Oxidation occurs at cathode and reduction occurs at anode.

Complete Step by step answer:(i) During electrolytic refining of copper, the anode is the positive electrode and is made from impure copper blocks. The electrolyte is a mixture of copper sulphate and sulphuric acid. The negative electrode is cathode. It is made from pure copper.
Thus, the cathode is made up of pure copper.

(ii) During electrolysis, copper sulphate dissociates to provide cupric ions and sulphate ions. At cathode, these cupric ions get discharged by gaining electrons from the cathode.
The removal of the concentrated copper metal from the cathode is made easier by coating the cathode with graphite.
The impurities from impure copper metal of anode combine with sulphate ions to form metal sulphates. These metal sulphates dissolve in the electrolytic solution. Certain impurities such as silver and gold do not dissolve in the electrolyte and settle down as the anode mud (sludge or dust).
The reaction that takes place at the anode is the oxidation of copper metal to cupric ions.
 $$\text{Cu }\to \text{ C}{\text{u}}^{2+}+2e^{-}$$

Note: Blister copper has purity of around 98 to 99 percent. You can increase the percent purity of copper to 99.95 by using an electro-refining method. You can use the highly pure copper metal in electrical components.