Chapter 3, Problem 26RQ

Summary Introduction

Interpretation:

At the pH of $7.4$, the ratio of dihydrogen phosphate $\left({\text{H}}_{\text{2}}{\text{PO}}_4^{-}\right)$ to hydrogen phosphate $\left({\text{H}}_{\text{2}}{\text{PO}}_4^{-}\right)$ in blood is to be calculated.

Concept introduction:

A buffer solution is the mixture of a weak acid along with its conjugate base or vice versa. The pH of the buffer solution does not changeappreciably with the addition of any strong acid or base in the buffer solution. The Henderson–Hasselbalch expression is used to calculate the pH of a weak acid and its conjugate base. Mathematically, it is represented as:

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

Here, pH is the measure of the acidity of the solution, $\text{p}{K}_{\text{a}}$ is the negative logarithm of the dissociation constant, $\left[\text{HA}\right]$ is the concentration of weak acid, and $\left[{\text{A}}^{-}\right]$ is the concentration of its conjugate base.