Chapter 20, Problem 112IE

Interpretation Introduction

Interpretation: The value of ${\text{pK}}_{\text{a}}$ of benzoic acid is to be calculated.

Concept introduction: Benzoic acid is a weak acid that partially dissociates into ions. The solution of benzoic acid with sodium benzoate forms a buffer in which the ${\text{pK}}_{\text{a}}$ of benzoic acid is calculated by the formula,

${\text{pK}}_{\text{a}}=\text{pH}-\log \frac{\left[{\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{COONa}\right]}{\left[{\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{COOH}\right]}$

To determine: The value of ${\text{pK}}_{\text{a}}$ of benzoic acid.