Gujarat BoardEnglish MediumSTD 10Sciencemetals and non-metals4 Marks
Question
Describe the electrolytic refining method for the purification of metals.
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Answer
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.
[Electrolytic refining of copper]
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.
For example,
At anode (+): $Cu ( s ) \rightarrow Cu ^{2+}( aq )+2 e ^{-}$ (Impure)
At cathode (-): $Cu ^{2+}( aq )+2 e ^{-} \rightarrow Cu ( s )$ (Pure)
Net reaction: $Cu ( s ) \rightarrow Cu ( s )$ (Impure) (Pure)
The soluble impurities pass into the solution while the insoluble impurities such as gold, silver, platinum are settled at the bottom of the anode and are called anode-mud.
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