(i) BeO is almost insoluble in water as it is covalent in nature and tightly held together in the solid state while BeSO4 is highly soluble in water due to high energy of solvation of smaller Be2+ ion.
(ii) The size of O2– ion is much smaller than that of the SO42− ion. Since a bigger anion stabilises a bigger cation more than a smaller anion therefore, the lattice energy of BaO is much smaller than that of BaSO4 and hence BaO is soluble while BaSO4 is insoluble in water.
(iii) LiI having much more covalent character than KI because of small size of Li+ as compared to K+. Hence, LiI is more soluble in ethanol.