Question

During the electrolysis of copper(ll) sulphate solution using platinum as cathode and carbon as anode. What change is noticed in the electrolyte?

Answer 1

During the electrolysis of copper (II) sulphate (${\mathrm{CuSO}}_4$ ) solution using platinum as cathode and carbon as anode, copper sulphate gives copper and sulphate ions.

Electrolysis of copper sulphate solution:

$$\begin{gathered} {\mathrm{CuSO}}_4\left(aq\right)\rightleftharpoons {\mathrm{Cu}}^{2+}\left(aq\right)+{\mathrm{SO}}_4^{2-}\left(aq\right) \\ (coppercopperionsulphateion \\ sulphate) \\ {\mathrm{H}}_2\mathrm{O}\left(l\right)\rightleftharpoons {\mathrm{H}}^{+}\left(aq\right)+{\mathrm{OH}}^{-}\left(aq\right) \\ waterprotonhydroxideion \end{gathered}$$

At anode: oxidation of copper atom occur by loses of electrons.

$\mathrm{Cu}-2{\mathrm{e}}^{-}\to {\mathrm{Cu}}^{2+}$

At ctode: reduction of copper ions is done by gain of electrons.

${\mathrm{Cu}}^{2+}+2{\mathrm{e}}^{-}\to \mathrm{Cu}$

The blue color of the copper sulphate $CuS{O}_4$solution becomes disappear due to decrease in the concentration of ${\mathrm{Cu}}^{2+}$ions in the solution because they deposited at the anode and a colorless solution is obtained when electrolysed by platinum electrodes.