Question

The electrolyte used for refining of copper is:
A.Copper nitrate
B.Copper citrate
C.Copper sulphate
D.Carbon

Answer 1

Hint: The electrolyte used in electrolytic refining of copper must have the copper ion so that it can be deposited as pure copper. i.e., the electrolyte must be a solution of a soluble salt of copper metal. The electrolyte used for copper refining has a polyatomic anion carrying an overall charge of -2.

Complete step by step answer:
The process of purifying the crude metals is called refining. A large number of metals such as copper, silver, aluminium, zinc, gold, lead, etc., are refined by the method of electrolytic refining.
In electrolytic refining, the impure metal is taken as the anode and cathode is made up of a pure strip of the same metal.
In case of electrolytic refining of copper, blister copper is the crude copper metal as it is an impure form of copper containing sulphur and so it is made anode. A thin sheet of pure copper is made the cathode while copper sulphate solution (which is a solution of a soluble sulphate salt of copper) acidified with sulphuric acid is taken as the electrolyte.
When electric current is passed, copper ions from the electrolyte are deposited at the cathode in the form of pure copper metal while an equivalent amount of copper dissolves from the anode and goes into the electrolyte as copper ions.
Anode: ${\text{Cu}}\left( {\text{s}} \right) \to {\text{C}}{{\text{u}}^{2 + }}\left( {{\text{aq}}} \right) + 2{{\text{e}}^{\text{ - }}}$
Cathode: ${\text{C}}{{\text{u}}^{2 + }}\left( {{\text{aq}}} \right) + 2{{\text{e}}^{\text{ - }}} \to {\text{Cu}}\left( {\text{s}} \right)$
The net result of electrolysis of copper is the transfer of copper in pure form from the anode to the cathode.
The impurities of iron, nickel, zinc and cobalt present in blister copper being more electropositive pass into the solution as soluble sulphates while the impurities of antimony, selenium, platinum being less electropositive are not affected by the copper sulphate solution and so settle down as anode mud.
Hence, the electrolyte used for refining of copper is copper sulphate solution and

so option C is correct.

Note: Most of the ores of copper are copper sulphides. These sulphide ores are converted into oxides by roasting and then to metallic copper by a reducing agent. During smelting, copper is obtained in the form of molten copper matte. This copper matte is then used to obtain pure copper by electrolysis.
The recovery of precious metals like silver, gold and platinum from the anode mud more than compensates for the high cost of electrolytic refining. Copper thus obtained is about 99 percent pure.