Question

During electrolysis of acidulated water, which gas is collected at cathode and which gas is collected at anode?

• A. Hydrogen, Oxygen
• B. Oxygen, Hydrogen
• C. Hydronium, Hydroxyl
• D. None of the above

Answer 1

The correct option is A Hydrogen, Oxygen

Acidulated water is water where some sort of acid is added.

Ionization of acidified water:

$H_{2}O\leftrightharpoons H^{+}+O{H}^{-}$

$H_{2}S{O}_4\leftrightharpoons 2H^{+}+S{O}_4^{2-}$

Ions present in solution are $S{O}_4^{2-}$, $O{H}^{-}$ and $H^{+}$

+ve charge move towards cathode whereas -ve charge move towards anode.

Reaction at cathode:

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

$H+H\to H_2$

Reaction at anode

$O{H}^{-}$ ion discharge in preference to $S{O}_4^{2-}$

$O{H}^{-}\to OH+e^{-}$

$4OH\to 2H_{2}O+O_2$

Hence, during electrolysis of acidulated water, hydrogen is collected at cathode and oxygen is collected at anode.