Question

Which alkali metal has maximum degree of hydration?

Answer 1

1. Hydration enthalpy is the amount of energy released on dissolution of one mole of gaseous atom.
2. It is inversely proportional to the ionic size of atom. That means, with increase in ionic size, hydration enthalpy decreases.
3. Therefore, Li has the maximum degree of hydration.
4. The order of hydration of alkali metals is as follows -${\mathrm{Li}}^{+}>{\mathrm{Na}}^{+}>{\mathrm{K}}^{+}>{\mathrm{Rb}}^{+}>{\mathrm{Cs}}^{+}$
5. This is the reason lithium salts are mostly hydrated, for example: $\mathrm{LiCl}.2{\mathrm{H}}_2\mathrm{O}$.