describe electrolytic refining method for the purification of copper {3 mark question}
Answers
Answer:
The metal obtained by reduction method is not very pure. The method to obtain about hundred percent pure metal by removing impurities present in very small amounts in the metal is called refining.
Refining of copper metal is carried out by the electrolysis method: The rod of impure copper is arranged as the anode and the rod of pure copper is arranged as a cathode. The aqueous solution of copper sulphate is taken as the electrolyte. A little dilute sulphuric acid is added to it. When an electric current is passed through the electrolyte, the proportion in which copper from the anode is dissolved in aqueous solution of copper sulphate, copper in the same proportion from copper sulphate solution is deposited at the cathode. Thus, the copper deposited at the cathode in this way has almost 100% purity.
Anode (Positive pole): Cu(s) (Impure) → Cu
2
+(aq)+2e
−
(oxidation)
Cathode (Negative pole): Cu
2+
(aq) + 2e- → Cu(s) (reduction)
Net reaction: Cu(s) (Impure) → Cu(s) (Pure)
Explanation:
The metals obtained from their ores are not very pure. Hence, it is essential to purify the metals. The most widely used method for refining impure metals is electrolytic refining.
Metals such as copper, zinc, tin, nickel, silver and gold are refined by electrolytic process. In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. The apparatus is set up as shown in the figure On passing the electric current through the electrolyte, the pure metal from the anode dissolves into electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode.