Question

The hydration energy of $M{g}^{2+}$ is larger than that of

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

Answer 1

Answer: (B)

$N{a}^{+}$

Hydration energy depends on ionic radii and radii decreases as we move along column from left to right and increases down the group, also as positive charge increases, radii dereases. As radii increases, hydration energy decreases. So among all given options only sodium ion has bigger radii than $M{g}^{+2}$ so it has lower hydration energy than $M{g}^{+2}$. Hydration energy of $N{a}^{+}=-435$ KJ/mol. Hydration energy of $M{g}^{+2}=-1921$ KJ/mol.