Question

The aqueous solution of one of the following salts will turn phenolphthalein indicator pink. This salt is:

Options

• KCl

• K₂SO₄

• K₂CO₃

• KNO₃

Answer 1

K₂CO₃

Explanation:

Phenolphthalein turns pink only in a basic (alkaline) solution with a pH greater than 8.2. Potassium carbonate (K₂CO₃) is a basic salt formed from a strong base (KOH) and a weak acid (H₂CO₃). When dissolved in water, it undergoes anionic hydrolysis, releasing excess hydroxide ions (OH⁻), thereby increasing the pH and triggering the pink colour change.