The lattice energy of solid NaCl is 180 K.Cal per. mole. The dissolution of the solid in water in the form of ions is endothermic to the extent of 1KCal per. mole. if the solvation energies of Na+ and Cl- are in the ratio 6 : 5 , what is the enthalpy of hydration of sodium ion? the answer is given as -97.5 Kcal/ mole . how is this possible can any one help me