Which of the following salts is slightly soluble in water?

Correct Answer: CaSO₄

Explanation:

• AgCl (Silver chloride): Practically insoluble in water. It precipitates out almost completely.
• CaSO₄ (Calcium sulphate): Only slightly soluble in water. This is why hard water often contains calcium sulphate in small amounts.
• Na₂CO₃ (Sodium carbonate): Highly soluble in water, not slightly soluble.
• PbCl₂ (Lead(II) chloride): Very sparingly soluble in cold water, but its solubility increases in hot water. Still, in this context, it is classified as poorly soluble rather than slightly soluble.

Among the options, the salt that is slightly soluble in water is CaSO₄.