While performing a thermodynamics experiment, a student made the following observations,
$ \begin{aligned} & \mathrm{HCl}+\mathrm{NaOH} \rightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} \Delta \mathrm{H}=-57.3 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \mathrm{CH}_3 \mathrm{COOH}+\mathrm{NaOH} \rightarrow \mathrm{CH}_3 \mathrm{COONa}+\mathrm{H}_2 \mathrm{O} \\ & \Delta \mathrm{H}=-55.3 \mathrm{~kJ} \mathrm{~mol}^{-1} . \end{aligned} $
The enthalpy of ionization of $\mathrm{CH}_3 \mathrm{COOH}$ as calculated by the student is $\_\_\_\_$ $\mathrm{kJ} \mathrm{mol}^{-1}$. (nearest integer)