Which one of the following alkaline earth metal sulphates has its hydration enthalpy greater than its lattice enthalpy?

Answer: B::C::DSolution: As we move down the group, size of metal increases. Be has lower size while $S{O}_{2-}$ has bigger size, that's why $BeS{O}_4$ breaks easily and lattice energy becomes smaller but due to lower size of $Be$, water molecules are gathered around and hence hydration energy increases on the other hand, rest of the metals, i.e. $Ca,Ba,Sr$ have bigger size and that's why lattice energy is greater than hydration energy.
Time Saving Technique : In the question of finding hydration energy only check the size of atom. Smaller sized atom has more hydration energy. Thus, in this question $Be$ is placed upper most in the group has lesser size and not comparable with the size of sulphates. Hene, $BeS{O}_4$ is the right response.