Question

How is copper extracted from its sulphide ore? Explain the various steps supported by chemical equations. Draw labelled diagram for the electrolytic refining of copper.

Answer 1

Copper is a metal that is present low in the reactivity series. It mainly occurs in nature in the form of sulphide ore which can be converted into the corresponding oxide simply by heating in the absence of air, a process known as roasting. The obtained oxide is then reduced with carbon or any other suitable reducing agent to obtain the metal. 

2Cu₂S + 3O₂ → 2Cu₂O + 2SO₂

 2Cu₂O + Cu₂S → 6Cu + SO₂

The obtained metal is then purified by electrolytic refining.

In the purification of copper by electrolytic refining, the strip of impure copper metal is made the anode and a strip of pure copper metal is the cathode. A solution of copper sulphate is used as the electrolyte. When current is passed through the electrolyte, pure copper from the anode dissolves in the electrolyte. An equivalent amount of pure copper from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, where as the insoluble impurities remain in the solution and are deposited at the bottom of anode as anode mud.

Following reactions take place at anode and cathode

Anode : `Cu -> Cu^(+2) + 2e^(-)`

Cathode : `Cu^(+2) + 2e -> Cu`