Question

(a)Licl is hydrated, but NaCl is always anhydrous. Why ?
(b) Why is it that although $L{i}^{+}$ is far smaller than the othe metals ions, it moves through a solution less rapidly than the others ?

Answer 1

Hydration energy is inversely proportional to the size. Size of $L{i}^{+}$ is smaller than the $N{a}^{+}$so hydration energy of lithium is greater than that of sodium so LiCl is hydrated while NaCl is anhydrous.

The positive charge density around $L{i}^{+}$ion is quite high due to its very small size. It can attract several layers of water molecules and gets highly hydrated. Thus, $L{i}^{+}$ion is bigger in size compared with other alkali metal ions which are less hydrated. As a result, it moves through the aqueous solution less rapidly compared with ions of other alkali metals