If N a + ion is larger than M g 2 + ion and S 2 - is larger than C l - ion, which of the following will be least soluble in water?

Step-by-step solution

Higher the lattice energy lower the solubility. Out of the four combinations possible, the lattice energy of MgS (bi-bivalent ionic solid) is higher than those of N a 2 S , M g C l 2 (uni-bivalent or biuni-valent ionic solids ) and NaCl (univalent ionic solids) and hence, MgS is the least soluble. Thus, due to higher charge/ion, the lattice formed between Mg 2+ and S 2- is very strong. As lattice energy overweighs the hydration energy here, the salt is least soluble.