Ammonia gas evolution from ammonium ion neutralization

Steps:

• Identify reactants: solid (NH₄)₂SO₄ and excess NaOH solution.
• Balance equation: (NH₄)₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O + 2NH₃(g), with heating driving off NH₃.
• Note key process: NH₄⁺ acts as weak acid, reacting with OH⁻ base to release ammonia.
• Classify reaction: proton transfer defines it as acid-base.

Why A is correct:

• Acid-base reactions feature proton (H⁺) donation; NH₄⁺ donates H⁺ to OH⁻, forming NH₃ and H₂O per Brønsted-Lowry definition.

Why the others are wrong:

• B: No solid precipitate forms; products are soluble Na₂SO₄, water, and gaseous NH₃.
• C: Oxidation states unchanged (N stays +3 in NH₄⁺ and NH₃); no electron transfer.
• D: Involves two compounds reacting, not single-compound breakdown by heat alone.

Final answer: A