Question

With the help of a diagram explain the method of refining of copper by electrolysis.

Answer 1

Apparatus:

• The anode or the positive electrode comprises the block of impure copper.
• The cathode or the negative electrode comprises pure copper tubes.
• Copper sulphate (${\mathrm{CuSO}}_4$) acidified with Sulphuric acid(${\mathrm{H}}_2{\mathrm{SO}}_4$) acts as a graphite-coated electrolyte.

Mechanism:

• During the process of electrolysis, Copper sulphate solution dissociates into Copper ions(${\mathrm{Cu}}^{2+}$) and Sulphate ions(${{\mathrm{SO}}_4}^{2-}$).
• There is a movement of ${\mathrm{Cu}}^{2+}$ ions towards the negative electrode or cathode made of pure Copper and there is an equivalent deposition of pure Copper from the electrolyte to the cathode.
• The soluble impurities get dissolved into the solution while insoluble impurities get deposited at the bottom of the anode as anode mud.

Chemical reactions involved:

• At the anode, Oxidation of Copper takes place.

$\mathrm{Cu}\left(\mathrm{s}\right)\to {\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}$

• At the cathode, Reduction of Copper takes place.

${\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}\to \mathrm{Cu}\left(\mathrm{s}\right)$

Inference:

Hence, the refining of copper takes place by electrolysis.