Chapter 16, Problem 16.111SP

Interpretation Introduction

Interpretation:

Thevalue of $\text{pH}$ and the concentrations of all elements

$\left({\text{H}}_{\text{2}}{\text{C}}_{\text{8}}{\text{H}}_{\text{4}}{\text{O}}_{\text{4}}{\text{,HC}}_{\text{8}}{\text{H}}_{\text{4}}{\text{O}}_{\text{4}}{}^{\text{-}}{\text{, C}}_{\text{8}}{\text{H}}_{\text{4}}{\text{O}}_{\text{4}}{}^{\text{2-}}{\text{, H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{,OH}}^{\text{-}}\right)$ for $\text{0}{\text{.0250M H}}_{\text{2}}{\text{C}}_8{\text{H}}_4{\text{O}}_4$ needs to be determined.

Concept introduction:

A weak acid does not dissociate completely into hydrogen ion and conjugate base. The dissociation of a weak acid is represented as follows:

$\text{HA}\rightleftharpoons {\text{H}}^{+}+{\text{A}}^{-}$

The 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 concentrations of hydrogen ion, conjugate base and weak acid.

Also, pH of solution is calculated follows:

$\text{pH=-log}\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$ or $\left[{\text{H}}^{+}\right]$ is the concentration of hydrogen ion in the solution.