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Question:

The correct order of solubility of the following compounds in water is:

Ca(OH)2=Mg(OH)2

Ba(OH)2<Mg(OH)2

BaCO3>CaCO3

CaSO4<MgSO4

Solution:

With increase in the size of the central metal ion, the solubility of the sulphates of alkaline earth metals decreases as the hydration enthalpy from Be2+ to Ba2+ decreases down the group. Therefore, MgSO4 is more soluble in water than CaSO4.