Chapter 16, Problem 18QP

Interpretation Introduction

Interpretation:

The reaction that represents the auto-ionization of water is to be determined.

Concept introduction:

Water is a universal solvent and a very weak electrolyte, which undergoes ionization to a very small extent.

Water being an amphoteric species acts both as an acid and a base and undergoes auto-ionization, as shown in the reaction:

${\text{H}}_2\text{O(}l)+{\text{H}}_2\text{O(}l\text{)}\rightleftharpoons {\text{H}}_3{\text{O}}^{+}(aq)+{\text{OH}}^{-}(aq)$

Water undergoes self-ionization and being a weak electrolyte, dissociates partially into its constituent ions $\left[{\text{H}}_3{\text{O}}^{+}\right]$ and $\left[{\text{OH}}^{-}\right]$. The equilibrium expression for the auto-ionization of water is as follows:

$K_{\text{w}}=\left[{\text{H}}_3{\text{O}}^{+}\right]\left[{\text{OH}}^{-}\right]$

Acids and bases react together to neutralize each other and form their conjugate base and conjugate acid, respectively.

$\text{Acid}+\text{Base}\rightleftharpoons \text{conjugate base}+\text{conjugate acid}$ …… (1)