Heat of solution of BaCl₂.2H₂O - 200 kJ mol^-1
Heat of hydration of BaCl₂ = - 150 kJ mol^-1
Hence heat of solution of BaCl₂ is

We have 

$\begin{array}{l}{\mathrm{BaCl}}_2\cdot 2{\mathrm{H}}_2\mathrm{O}+\mathrm{aq}\to {\mathrm{Ba}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O};\\ \mathrm{\Delta }H=200\mathrm{kJ}{\mathrm{mol}}^{-1}\\ {\mathrm{BaCl}}_2+2{\mathrm{H}}_2\mathrm{O}\to {\mathrm{BaCl}}_2\cdot 2{\mathrm{H}}_2\mathrm{O};\mathrm{\Delta }\dot{H}=-150\mathrm{kJ}{\mathrm{mol}}^{-1}\end{array}$

On adding both equation we get

${\mathrm{BaCl}}_2+\mathrm{aq}\to {\mathrm{Ba}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\mathrm{\Delta }H=50\mathrm{kJ}{\mathrm{mol}}^{-1}$

This is the reaction for dissolution of BaCl₂. Therefore heat of this reactions is in fact the heat of solution of BaCl₂.