Question

When an aqueous solution of $H_{2}S{O}_4$ is electrolysed, the product at anode is

• A. $H_2$
• B. $O{H}^{-}$
• C. $S{O}_4^{2-}$
• D. $O_2$

Answer 1

The correct option is D $O_2$

In aqueous solution, dilute sulphuric acid dissociates to form protons and sulphate ions. Also, the autoionisation of water gives protons and hydroxide ions. Thus, the dilute aqueous sulphuric acid solution contains protons, hydroxide ions and sulphate ions.
$H_{2}S{O}_4\left(aq\right)\to 2H^{+}\left(aq\right)+S{O}_4^{2-}\left(aq\right)H_{2}O\left(l\right)\to H^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$

Anode is a positive electrode. It attracts hydroxide ions and sulphate ions. At anode, hydroxide ions get discharged (in preference to sulphate ions) to form oxygen gas.

$4O{H}^{-}\left(aq\right)\to 2H_{2}O\left(l\right)+O_2\left(g\right)+4e^{-}$