Properties and reactions of ammonia

Steps:

• Analyze ammonia's Lewis structure: N bonded to 3 H atoms with 1 lone pair.
• Determine pH change from NH3 dissolving in water via its basic reaction.
• Check if (NH4)2SO4 + HCl produces NH3 gas upon warming.
• Observe that option D lacks content, preventing full evaluation.

Why B is correct:

• Ammonia is a weak base that reacts with water to form OH⁻ ions (NH₃ + H₂O ⇌ NH₄⁺ + OH⁻), raising pH per the Arrhenius definition of bases.

Why the others are wrong:

• A: Ammonia has three bond pairs and one lone pair, making this statement correct, but it may not align with single-choice intent.
• C: Warming (NH₄)₂SO₄ with aqueous HCl yields (NH₄)₂SO₄ remains or forms NH₄Cl and H₂SO₄; no NH₃ gas evolves—requires a base like NaOH.
• D: Not enough information.

Final answer: B