Question

Write down the ionic equation for the reactions that take place at the cathode during electrolysis of acidified water.

Answer 1

Cathode Reaction during electrolysis of acidified water

• Hydrogen ions, ${\mathrm{H}}^{+}$ being the only positively charged ions, migrate to the cathode. since the cathode is a reservoir of electrons, ${\mathrm{H}}^{+}$gains an electron and becomes a neutral hydrogen atom

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

• Hydrogen atoms combine to form a molecule and this comes out as a hydrogen gas

$\mathrm{H}+\mathrm{H}\to {\mathrm{H}}_2$

• Since ${{\mathrm{SO}}_4}^{-2}$ ions migrate to the anode, and ${\mathrm{H}}^{+}$ions have been discharged, the concentration of the sulphuric acid will decrease.
• Product at the cathode: 2 volumes of hydrogen gas