Chemistry - PERIODIC TABLE Question with Solution | TestHub

Question Explanation:

Solubility decrease down a group due to energy changes.

Concept:

Lattice vs. Hydration Enthalpy Trends.

Solution:

Solubility is determined by the balance between hydration energy and lattice energy. As we move down the group for alkaline metal carbonates, both energies decrease because the cation size increases. However, the hydration energy decreases much more rapidly than the lattice energy. Because the energy released by hydration becomes insufficient to break the lattice, solubility decreases.

Solubility $\propto \frac{\Delta {\mathrm{H}}_{\text{hydration }}}{\text{ Lattice Energy }}$

Final Answer: Hydration energy rapidly decreases and lattice energy gradually on moving down the group.