The standard heat of formation, in kcal/mol of \(Ba^{2+}\) is: [Given : standard heat of formation of \(\text{So}^{2-}_4\) ion (aq) = - 216 kcal/mol, standard heat of crystallisation of \(\text{BaSO}_4(s)\) = - 4.5 kcal/mol, standard heat of formation of \(\text{ BaSO}_4(s)\) = - 349 kcal/mol]