Thermodynamics

The standard heat of formation, in kcal/mol, of $\mathrm{B}{\mathrm{a}}^{2+}$ is: [Given: standard heat of formation of the $\mathrm{S}{\mathrm{O}}_4^{2-}$ ion (aq) = –216 kcal/mol, standard heat of crystallisation of $\mathrm{BaS}{\mathrm{O}}_4(\mathrm{s})$ = –4.5 kcal/mol, standard heat of formation of $\mathrm{BaS}{\mathrm{O}}_4(\mathrm{s})$ = –349 kcal/mol]