If Na+ ion is larger than Mg2 + ion and S2 - is larger than Cl- ion, which of the following will be least soluble in water?

Question

If Na+ ion is larger than Mg2 + ion and S2 - is larger than Cl- ion, which of the following will be least soluble in water? (A) Sodium chloride (B) Sodium sulphide (C) Magnesium chloride (D) Magnesium sulphide

Tardigrade Admin · Accepted Answer

Higher is the lattice energy lower is the solubility. Out of the four combinations possible, the lattice energy of

M g S

(bi-bivalent ionic solid) is higher than those of

N a_{2} S, M g C l_{2}

and

N a Cl

(univalent ionic solids) and hence,

M g S

is the least soluble. Thus, due to higher charge/ion, the lattice formed between

M g^{2 +}

and

S^{2 -}

is very strong.
As lattice energy overweighs the hydration energy here, the salt is least soluble.

Q. If Na+ ion is larger than Mg2+ ion and S2− is larger than Cl− ion, which of the following will be least soluble in water?

Sodium chloride

Sodium sulphide

Magnesium chloride

Magnesium sulphide

Q. 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?