Question

During the electrolysis of an aqueous solution $NaCl$, hydrogen ion is reduced at the cathode and not the sodium ion through both $N{a}^{+}$ and $H^{+}$ ions are present inn the solution, why?

Answer 1

Sodium chloride $\left(NaCl\right)$ and water $\left(H_{2}O\right)$ ionize as follows :

$NaCl\rightleftharpoons {Na}^{+}+{Cl}^{-}$ and $H_{2}O\rightleftharpoons H^{+}+{OH}^{-}$

At cathode

Both ${Na}^{+}$ and $H^{+}$ are present near the cathode. But the discharge potential of $H^{+}$ is lower than that of ${Na}^{+}$ ion. So $H^{+}$ ions are discharged in preference to ${Na}^{+}$ ions.

$H^{+}+e^{-}⟶H$

$H+H⟶H_2$

Thus $H_2$ gas is liberated at the cathode and ${Na}^{+}$ remain in the solution.