Chapter 22, Problem 11STP

To determine

The number of hydronium ions the substance forms in water.

Explanation of Solution

Introduction:

When dissolved in water, one molecule of ${\text{H}}_2\text{S}$ reacts with one molecule of water to give a ${\text{HS}}^{-}$ ion and a ${\text{H}}_3{\text{O}}^{+}$ ion.

The chemical formula of the substance is ${\text{H}}_2\text{S}$ . Its chemical name is hydrogen sulphide.

When dissolved in water, one molecule of ${\text{H}}_2\text{S}$ reacts with one molecule of water to give an ${\text{HS}}^{-}$ ion and a ${\text{H}}_3{\text{O}}^{+}$ ion. The ${\text{HS}}^{-}$ ion further reacts with another water molecule to produce an ${\text{S}}^{-}$ ion and a ${\text{H}}_3{\text{O}}^{+}$ ion.

  $\begin{array}{l}{\text{H}}_2{\text{S+H}}_2\text{O}\to {\text{HS}}^{-}+{\text{H}}_3{\text{O}}^{+}\\ {\text{HS}}^{-}{\text{+H}}_2\text{O}\to {\text{ S}}^{-}+{\text{H}}_3{\text{O}}^{+}\end{array}$

Thus, one molecule of ${\text{H}}_2\text{S}$ produces two ${\text{H}}_3{\text{O}}^{+}$ ions.

Conclusion: A molecule of ${\text{H}}_2\text{S}$ produces two ${\text{H}}_3{\text{O}}^{+}$ ions in water.