Chapter 16, Problem 16.147MP

Interpretation Introduction

Interpretation:

The value of $\text{pH}$ and concentrations of all species needs to be determined.

Concept introduction:

For a weak acid say HA, the dissociation reaction is represented as follows:

$\text{HA}\left(aq\right)\rightleftharpoons {\text{H}}^{+}\left(aq\right)+{\text{A}}^{-}\left(aq\right)$

The expression for acid dissociation constant can be represented as follows:

$K_a=\frac{\left[{\text{H}}^{+}\right]\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$

Here, $\left[{\text{H}}^{+}\right]$, $\left[{\text{A}}^{-}\right]$ and $\left[\text{HA}\right]$ are equilibrium concentrations of hydrogen ion, concentration of conjugate base of HA and concentration of weak acid HA respectively.

The pH of the solution can be calculated as follows:

$\text{pH}=-\log \left[{\text{H}}^{+}\right]$

Here, $\left[{\text{H}}^{+}\right]$ is the concentration of hydrogen ion in the solution.