Question

Which one is not soluble in water?

• A. $NaCl$
• B. ${Na}_2{SO}_4$
• C. ${BaCl}_2$
• D. ${BaSO}_4$

Answer 1

The correct option is D

${\mathrm{BaSO}}_4$

Solubility decreases down the group due to a decrease in charge density.

Explanation for the correct option:

To be soluble in water, the energy of hydration should be more than the Lattice energy.

Barium sulphate (${\mathrm{BaSO}}_4$) is insoluble in water due to higher lattice energy.

Explanation for the incorrect option:

Sodium chloride ($\mathrm{NaCl}$), Sodium sulphate (${\mathrm{Na}}_2{\mathrm{SO}}_4$) and Barium chloride (${\mathrm{BaCl}}_2$) have higher hydration energy and are soluble in water.

Final answer:

Hence, option (D) is the correct option.