In determination of enthaply change of hydration of MgSO₄:
MgSO₄(s) + 7H₂O -> MgSO₄^.7H₂O(s)
It is impossible to measure the enthalpy change for this reaction. But, I don't know why?
Is it due to the activation energy of the reaction too high that cannot be overcome under standard conndition?

Besides, when M g of anhydrous magnesium sulphate(VI) were add to V cm³ of water in a beaker and all magnesium sulphate is dissolved, there was a maximum rise in temperature of the solution by T^oC. When calculating the enthalpy evolved by using E=mc (deltaT), what should I substitute for mass? Is mass  equal to the sum of mass of anhydrous magnesium sulphate(VI) and mass of water added?

Thank you.

In determination of enthaply change of hydration of MgSO₄:
MgSO₄(s) + 7H₂O -> MgSO₄^.7H₂O(s)
It is impossible to measure the enthalpy change for this reaction directly. But, I don't know why?
Is it due to the activation energy of the reaction too high that cannot be overcome under standard conndition?

In fact, I would like to ask this part.
I think the activation energy of the reaction is too high that cannot be overcome under standard condition. That means, the the reactants are kinetically stable.Is it right if I say so?