Question

Why the crystalline compounds of group 2 contains more water of crystallization than corresponding group1 compounds?

Answer 1

Dear student,
Actually, the existence of divalent cations in aqueous medium depends on hydration energy as higher hydration energy balances the higher value of second ionization energy.
In this way we know that, the hydration energy of group-2 elements are four to five times higher than the value of hydration energy of group -1 elements. It happens due to smaller size of gr.-1 elements and higher charge down the group which decreases hydration energy of gr-1 elements.
So, crystalline compounds of group-2 elements contain more water of crystallisation than the corresponding group 1 elements.