The standard molar enthalpy of combustion of carbon (grapnie at 25 c, 1 mole of mgso, was dissolved in water. the heat evolved was found to be 91.2 kj. one mole

The standard molar enthalpy of combustion of carbon (grapniE At 25 C, 1 mole of MgSO, was dissolved in water. the heat evolved was found to be 91.2 KJ. One mole of Mgso. 7H,O on dissolution gives a solution of the same composition accompanied by an absorption of 13.8 kJ. The enthalpy of hydration, i.e., AH for the reaction. MgSO,(s) + 7H,O() MgsO,.7H,O(s) is (A) -105 kJ/mol (B) -77.4 kJ/mol (C) 105 kJ/mol (D) None of these