Chapter 15, Problem 15.75SP

Interpretation Introduction

Interpretation:

The $K_a$ of the amino acid serine if it is $86.3\%$ dissociated at pH of $9.95$ has to be determined.

Concept Introduction:

Henderson-Hasselbalch equation is an equation which describes the derivation of pH as a measure of acidity in biological and chemical systems. This equation can be used to find the equilibrium pH in acid-base reaction and also for estimating the pH of a buffer solution.

$\text{pH}\text{=}{\text{pK}}_{\text{a}}\text{+}\text{log}\frac{\left[\text{Conjugate}\text{base}\right]}{\left[\text{Weak}\text{acid}\right]}$

$p{K}_a$ is analogues to pH and it is indicating the tendency of the compound to give up its proton. Lower $p{K}_a$ value stands for stronger acid.

A weak acid (it is partially dissociated in aqueous solution) equilibrium can be represented as follows,

$\underset{Weakacid}{HA}\underset{}{\rightleftarrows }{H}^{+}+{\underset{Conjugatebase}{A}}^{-}$