At `18^(@)C` the heat of solution of anhydrous `CuSO_(4)` in a large volume of water is -15.90 kcal per mole while that of `CuSO_(4).5H_(2)O` is 2.75 kcal per mole. What is the heat of hydration of `CuSO_(4)` ?

Explanation

Given that,
(i) `CuSO_(4)(s)+aq to CuSO_(4)(aq),DeltaH=-15.9 "kcal"`
(ii) `CuSO_(4).5H_(2)O+aq to CuSO_(4)(aq),DeltaH=+2.75 "kcal"`
We have to calculate `DeltaH` of the equation :
`CuSO_(4)(s)+aq to CuSO_(4).5H_(2)O,DeltaH=?`
Applying the inspection method, [Eqn (i)- Eqn (ii)],
We get, `CuSO_(4)(s)+aq to CuSO_(4).5H_(2)O,DeltaH=-15.9-2.75=-18.65 "kcal"`