Question

The salt whose aqueous solution will turn blue litmus to red is:
(a) ammonium sulphate
(b) sodium acetate
(c) sodium chloride
(d) potassium carbonate

Answer 1

 ammonium sulphate
Ammonium sulphate [(NH₄)₂SO₄] is formed from a weak base, ammonium hydroxide (NH₄OH), and a strong acid, sulphuric acid (H₂SO₄). On dissolving in water, (NH₄)₂SO₄ hydrolyses to form more H⁺ ions than OH^- ions. As the aqueous solution of the salt (NH₄)₂SO₄ is acidic, it turns blue litmus red.