Question

Arrange $N{a}^{+}$, $M{g}^{2+}$ and $A{l}^{3+}$ in increasing order of energy of hydration

• A. $N{a}^{+}<M{g}^{2+}<A{l}^{3+}$
• B. $A{l}^{3+}<M{g}^{2+}<N{a}^{+}$
• C. $A{l}^{3+}<N{a}^{+}<M{g}^{2+}$
• D. $M{g}^{2+}<A{l}^{3+}<N{a}^{+}$

Answer 1

Answer: (A)

The hydration enthaplies (ie, energies of hydration) of metal ions decreases with increase in ionic radii. Because of the smaller size of $A{l}^{3+}$ than $M{g}^{2+}$ and $N{a}^{+}$, its energy of hydration is larger than both these ions.

The order of heat of hydration is

$A{l}^{3+}>M{g}^{2+}>N{a}^{+}$