An aqueous solution of (NH4)2 SO4 is

Analyze the question: We are asked whether a solution of ammonium sulphate, (NH₄)₂SO₄, is acidic, alkaline, amphoteric or neutral. This is a salt hydrolysis question.

Concept: A salt's nature depends on the acid and base that formed it:

• Strong acid + strong base → neutral salt
• Strong acid + weak base → acidic salt
• Weak acid + strong base → alkaline (basic) salt

Solution:

1. (NH₄)₂SO₄ is formed from: • NH₃ (aq), i.e. NH₄OH, a weak base • H₂SO₄, a strong acid

2. In water, the salt dissociates completely: (NH₄)₂SO₄ → 2NH₄⁺ + SO₄²⁻

3. The sulphate ion comes from a strong acid, so it does not react with water (no hydrolysis).

4. The ammonium ion comes from a weak base, so it hydrolyses and releases H₃O⁺: NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺

5. Extra H₃O⁺ ions in solution means the pH falls below 7, so the solution is acidic.

Answer: A. Acidic

Exam tip: Remember "the stronger parent wins." Strong acid + weak base gives an acidic solution (e.g. NH₄Cl, (NH₄)₂SO₄, CuSO₄). Weak acid + strong base gives an alkaline solution (e.g. Na₂CO₃, CH₃COONa).