Question

(i) Explain why lithium salts are commonly hydrated and those of the other alkali metal ions usually anhydrous?

(ii) Write any two differences between lithium and other alkali metals.

Answer 1

(i) Lithium is the smallest in size among all the elements of the alkali metals groups. Hence, lithium ion can polarize water molecules more easily than other alkali metals. As a result, water molecules get attached to lithium salts as water of commonly hydrated. As the ionic size increases, their polarizing power decreases. So, other alkali metal ions are usually anhydrous.

(ii) (a) Lithium is least reactive but the strongest reducing agent among all the alkali metals.

(b) Lithium nitrates decompose to give the corresponding nitrite.

4LiNO₃ → 2Li₂O + 4NO₂ + O₂

2NaNO₃ → 2NaNO₂ + O₂