The solubility of the alkaline earth metal sulphates decrease down the group. While BeSO4 and MgSO4 are readily soluble in water, CaSO4, SrSO4, and BaSO4 are insoluble. This is because the greater hydration enthalpies of Be2+ and Mg2+ ions overcome the lattice enthalpy factor and therefore their sulphates are soluble in water. The hydration enthalpies of the rest compounds do not match the lattice enthalpy factor, thus making these sulphates insoluble in water.
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