Question

Which has more hydration energy? $MgS{O}_4$ or $Ba(S{O}_4$

• A.
• B.
• C. Same
• D. Data insufficient

Answer 1

The correct option is A

$△$$H_{hyd}$ = $\frac{k_1}{r_{+}}$ + $\frac{k_2}{r_{-}}$

observe that ${S{O}_4}^{2-}$ is a very big anion $\Rightarrow$ $r_{+}$ << $r_{-}$

Thus,hydration enthalpy $\alpha$ $\frac{1}{cationsize}$

$\therefore$ $MgS{O}_4$ has more hydration energy.

In cases where $r_{+}$ << $r_{-}$ lattice energy will not decreases rapidly with increases in cation size.But hydration energy will decrease rapdily with increasing cation size.

For solubility, hydration enthalpy > lattice energy.

$\therefore$ $MgS{O}_4$ is more soluble than $BaS{O}_4$