Chapter 2, Problem 9P

Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book.

Polyprotic Acids: Citric Acid Species at Various pHs Citric acid, a tricarboxylic acid important in intermediary metabolism, can be symbolized as H₃A. Its dissociation reactions are

$\begin{array}{l}{\text{H}}_3\text{A}\rightleftharpoons {\text{H}}^{+}+{\text{H}}_2{\text{A}}^{-}\text{p}{K}_1=3.13\\ {\text{H}}_2{\text{A}}^{-}\rightleftharpoons {\text{H}}^{+}+{\text{HA}}^{2-}\text{p}{K}_2=4.76\\ {\text{HA}}^{2-}\rightleftharpoons {\text{H}}^{+}+{\text{A}}^{3-}\text{p}{K}_3=6.40\end{array}$

If the total concentration of the acid and its anion forms is 0.02 M. what are the individual concentrations of H₃A, H₂A^-, HA^2-, and A^3- at pH 5-2?