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

We haveBaCl2.2H2O+aq → Ba2+aq+ 2Cl-aq + 2H2O; ∆H=200 kJ mol-1 BaCl2 +2H2O  → BaCl2 .2H2O; ∆H=-150 kJ mol-1On adding both equations, we getBaCl2  +aq → Ba2+aq+ 2Cl-aq; ∆H=50 kJ mol-1This is the reaction for dissolution of BaCl2. Therefore, heat of this reactions is in fact the heat of solution of BaCl2.