Question

On electrolysis of $CuS{O}_4$ solution in presence of platinum, the solution becomes colorless. Why?

Answer 1

1. During electrolysis, the Copper ions undergo reduction at the cathode producing Copper atom.
2. The blue of Copper sulfate solution($\mathit{C}\mathit{u}\mathit{S}{\mathit{O}}_{\mathbf{4}}$) is due to the presence of copper ions.
3. After electrolysis, the Copper ions are completely converted to Copper atoms the blue color of the solution will disappear.
4. The reaction is,

$$\begin{gathered} Cathode:\underset{Copperions}{C{u}^{2+}}+2e^{-}\to \underset{Copperatom}{Cu} \\ Anode:\underset{Hydroxideions}{2O{H}^{-}}\to H_{2}O+\frac{1}{2}{O}_2+2e^{-} \end{gathered}$$

So, the blue color of the solution disappears due to the formation of the Copper atom by the reduction of copper ions at the cathode electrode.