Solubility of the compounds of s-block elements depends on the magnitude of lattice enthalpy and hydration enthalpy. The least soluble sulphate of second group elements is

In the case of BeSO4 and MgSO4, hydration enthalpy dominates lattice enthalpy;Both are soluble in water ;Down the group lattice enthalpy almost remains constant but hydration enthalpy decreases, thus solubility decreases.BaSO4 is least soluble;