Chemistry - CHEMICAL BONDING Question with Solution | TestHub

The solubility of ionic compounds depends on lattice energy and hydration energy.

A. For alkali metal carbonates, as cation size increases down the group (Li to Cs), lattice energy decreases more significantly than hydration energy, leading to increased solubility. So, ${\mathrm{Li}}_2{\mathrm{CO}}_3<{\mathrm{Na}}_2{\mathrm{CO}}_3<{\mathrm{K}}_2{\mathrm{CO}}_3<{\mathrm{Rb}}_2{\mathrm{CO}}_3<{\mathrm{Cs}}_2{\mathrm{CO}}_3$ is correct.

C. For alkaline earth metal oxalates, ${\mathrm{BeC}}_2{\mathrm{O}}_4$ is more soluble than ${\mathrm{BaC}}_2{\mathrm{O}}_4$. For smaller cations (like Be²⁺) with larger anions (like C₂O₄²⁻), hydration energy decreases less rapidly than lattice energy as cation size increases, leading to decreasing solubility down the group. Thus, ${\mathrm{BaC}}_2{\mathrm{O}}_4<{\mathrm{BeC}}_2{\mathrm{O}}_4$ is correct.