Question

Which of the following statements are correct regarding the process of electrolysis of water?

• A. ${\text{H}}^{+}$ ions move towards the cathode.
• B. ${\text{OH}}^{-}$ ions move towards the anode.
• C. Oxygen gas evolves at the cathode.
• D. Hydrogen gas evolves at the cathode.

Answer 1

Answer: (A), (B), (D)

Hydrogen gas evolves at the cathode.

During its electrolysis, the water molecule (${\text{H}}_2\text{O}$) undergoes decomposition to form ${\text{H}}^{+}$ and ${\text{OH}}^{-}$ ions.

The ${\text{H}}^{+}$ ions move towards the cathode (negatively charged electrode) and thus hydrogen gas evolves there. The reaction occuring at cathode is:

$2{\text{H}}_2\text{O (l)}+2{\text{e}}^{-}\to {\text{H}}_2\text{(g)}+2{\text{OH}}^{-}\text{(aq)}$

The ${\text{OH}}^{-}$ ions move towards the anode (positively charged electrode) and thus oxygen gas evolves there. The reaction occuring at anode is:

$2{\text{H}}_2\text{O (l)}\to {\text{O}}_2\text{(g)}+4{\text{H}}^{+}\text{(aq)}+4{\text{e}}^{-}$