Question

Explain hydronium ion. Write the ionisation of sulphuric acid showing the formation of hydronium ion.

Answer 1

Hydronium ion (${\mathrm{H}}_3{\mathrm{O}}^{+}$) is nothing but a water molecule with an extra hydrogen ion attached to it, i.e., (${\mathrm{H}}_2\mathrm{O}+{\mathrm{H}}^{+}\stackrel{}{\to }{\mathrm{H}}_3{\mathrm{O}}^{+}$).
Acids are proton donors. They produce ${\mathrm{H}}^{+}$ ions when dissolved in water. As these ${\mathrm{H}}^{+}$ ion​s are unstable and cannot exist freely, they combine with water molecules to form hydronium ions. Thus, acids ionise in water and form hydronium ions as the only positive ions. The ionisation of sulphuric acid in water results in the formation of hydronium and sulphate ions. The reaction is as follows:

$$\begin{gathered} {\mathrm{H}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O}\leftrightarrow 2{\mathrm{H}}_3{\mathrm{O}}^{+}+{\mathrm{SO}}_4^{2-} \\ \mathrm{Sulphuric}\mathrm{Water}\mathrm{Hydronium}\mathrm{ion}\mathrm{Sulphate}\mathrm{i}\mathrm{on} \\ \mathrm{a}\mathrm{cid} \end{gathered}$$