Enthalpy change

K2SO4(s) is an ionic compound.When K2SO4(s) is dissolved in water:K2SO4(s) à 2K+(aq) + SO42-(aq)△ Hsolu = △Hhydration -△HlatticeThe reaction divided into 2 parts:Part 1: -△Hlattice: K2SO4(s) à 2K+(g) + SO42-(g) (energy is required to break the lattice) which is resulted in an endothermic reaction. Part 2: △Hhydration: 2K+(g) + SO42-(g) à 2K+(aq) + SO42-(aq)When the gas state of substance dissolved into the water, the cations will be surrounded by the O atom in H2O molecules and the anions will be surrounded by the H atoms in H2O molecules. In this case, K+ will be surrounded by the O atom in H2O molecules and SO42- will be surrounded by the H atoms in H2O molecules. Thus, the attraction between the ion and molecules (a bonding is formed) resulted in an exothermic reaction. In conclude, according to your descriptions, -△Hlattice > △Hhydration, and finally an endothermic reaction occurs.