The solubilities of carbonates decrease down the magnesium group (alkaline earth metals) due to a decrease in:(AIEEE 2003 - EQUIVALENT TO IIT JEE MAIN)

1) lattice energies of solids

2) hydration energies of cations

3) inter-ionic attraction

4) entropy of solution formation

Ans : ( 2 )

Solubility of an ionic compound in water decreases with increase in lattice energy but increase with hydration energies.

In alkaline earth metal group, the hydration energy of cation decreases from top to bottom with increase in the size of cation. However, the lattice energy remains almost unchanged.