Chapter 7, Problem 90E

Interpretation Introduction

Interpretation : The pH of the phosphoric acid solution should be calculated.

Concept Introduction :

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

  $\text{HA}+{\text{H}}_{\text{2}}\text{O}\rightleftharpoons {\text{H}}_{\text{3}}{\text{O}}^{+}+{\text{A}}^{-}$

The acid dissociation constant for dissociation of an acid is represented as follows:

  $K_a=\frac{\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$

Dissociation equilibrium constants for H₃PO₄ are,

  $\begin{array}{l}{K}_{a1}=7.5\times {10}^{-3}\\ K_{a2}=6.2\times {10}^{-8}\\ K_{a3}=4.8\times {10}^{-13}\end{array}$