Chapter 12, Problem 12.140QP

The freezing point of 0.109 m aqueous formic acid is −0.210°C. Formic acid, HCHO₂, is partially dissociated according to the equation

${\text{HCHO}}_2(aq)\rightleftharpoons {\text{H}}^{+}(aq)+{\text{CHO}}_2{}^{-}(aq)$

Calculate the percentage of HCHO₂ molecules that are dissociated, assuming the equation for the freezing-point depression holds for the total concentration of molecules and ions in the solution.