Chapter 15, Problem 15.4A

APPLY 14.4 Lactic acid, which builds up in muscle tissue upon strenuous exercise, is partially dissociated in aqueous solution:

The following equilibrium concentrations were measured at 25°C:

Lactic acid $\left[{\text{C}}_3{\text{H}}_{\text{6}}{\text{O}}_3\right]=9.64\times {10}^{-2}\text{M;}\left[{\text{H}}^{\text{+}}\right]=3.65\times {10}^{-3}\text{M;}$

Lactate ion [C₃H₅O₃^-] = 3.65 × 10-3 M.

(a) Calculate the value of the equilibrium constant.

(b) What is the concentration of lactic acid (C₃H₆O₃) if at equilibrium

$\left[{\text{C}}_3{\text{H}}_{\text{6}}{\text{O}}_3{}^{-}\right]=\left[{\text{H}}^{\text{+}}\right]=1.17\times {10}^{-2}\text{M?}$