Question

An electrolytic cell is set up using two platinum electrodes and an aqueous solution of copper (II) sulphate. Name the spectator ion in the solution.

Answer 1

Electrolysis is a chemical process of dissociation of a compound into its elements by passing electric current in the aqueous or molten state.

Spectator ions are those ions which exist as a reactant and a product in a chemical equation.

Electrolysis of copper sulphate $\left({\mathrm{CuSO}}_4^{2-}\right)$ gives copper ions $\left({\mathrm{Cu}}^{2+}\right)$and sulphate ions $\left({\mathrm{SO}}_4^{2-}\right)$.

${\mathrm{CuSO}}_4\rightleftharpoons {\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right)$

Water will get ionized into hydrogen ion$\left({\mathrm{H}}^{+}\right)$ and hydroxide ion $\left({\mathrm{OH}}^{-}\right)$.

${\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{H}}^{+}+{\mathrm{OH}}^{-}$

1. Inert electrodes are used in the electrolysis of copper sulphate solution.

2. Sulphate ions does not participate in any change in the reaction during electrolysis.

Hence, sulphate ions $\left({\mathrm{SO}}_4^{2-}\right)$ are spectator ion in the solution.