Question

The aqueous solution of one of the following salts will turn red litmus to blue. This salt is:

Options

• potassium sulphate

• sodium sulphate

• sodium chloride

• potassium carbonate

Answer 1

Potassium carbonate     

Explanation:

Turning red litmus to blue requires a basic or alkaline solution. Potassium carbonate (K₂CO₃) is a basic salt formed from a strong base (KOH) and a weak acid (H₂CO₃). When dissolved in water, carbonate ions undergo anionic hydrolysis, releasing excess hydroxide ions (OH⁻), thereby raising the pH above 7 and turning red litmus paper blue.