How would you explain the given observations?
BeO is almost insoluble but `BeSO_4`, is soluble in water.

Explanation

`O^(2-)` is smaller in size than `SO_4^(2-)`. Consequently, small `Be^(2+)` ion is tightly packed with small `O^(-)` ion and thus, lattice enthalpy of BeO is greater than its hydration enthalpy. So BeO is insoluble in water. On the other hand, small `Be^(2+)` ion is loosely packed with large `SO_4^(2-)` ion and thus, lattice enthalpy of `BeSO_4` is less than its hydration enthalpy. So, `BeSO_4` is soluble in water.