Question

In which of the following the hydration energy is higher than the lattice energy?

• A. $SrSO_{4}$
• B. $BaSO_{4}$
• C. $MgSO_{4}$
• D. $RaSO_{4}$

Answer 1

Answer: (C)

$MgSO_{4}$

Answer 2

In case of $MgSO_{4}$ hydration energy is higher than the lattice energy. Hydration enthalpies of alkaline earth metal ions decrease with increase in ionic size down the group. Lattice energy also decreases as the size of cation increases. But in case of large size anion such as $SO_{4}^{2-}$ and the small changes in cation size do not alter the lattice energy, i.e., lattice energies are about the same. For $BeSO_{4}$ and $MgSO_{4}$ , hydration enthalpies of $Be^{2+}$ and $Mg^{2+}$ ions are higher than that of their lattice enthalpies.