Chapter 8, Problem 8.109P

Interpretation Introduction

Interpretation:

The ratio of ${\text{HPO}}_{\text{4}}{}^{2-}/{\text{H}}_{\text{2}}{\text{PO}}_4{}^{-}$ in a phosphate buffer of pH 7.9 (the pH of human pancreatic fluid) needs to be calculated.

Concept Introduction:

The pH of buffer solution is calculated using the following formula:

$\text{pH }={\text{ pK}}_{\text{a}}+\text{ log}\frac{\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$

This is known as Henderson- Hasselbalch equation. Here, $p{K}_{\text{a}}$ is negative log of acid dissociation constant, $\left[{\text{A}}^{-}\right]$ is concentration of conjugate base and $\left[\text{HA}\right]$ is concentration of acid.