Question

The aqueous solution of one of the following salts will turn phenolphthalein indicator pink. This salt is:
(a) KCl
(b) K₂SO₄
(c) K₂CO₃
(d) KNO₃

Answer 1

K₂CO₃
K₂CO₃ is formed from a weak acid, carbonic acid (H₂CO₃), and a strong base, potassium hydroxide (KOH). On hydrolysis, K₂CO₃ forms more OH^- ions than H⁺ ions, and thus, it is basic. As the aqueous solution of the salt is basic, it turns a phenolphthalein indicator pink.