Compound identification via chloride and ammonium tests

Steps:

• Solution K forms a dense white precipitate with AgNO3, indicating Cl⁻ ions (AgCl).
• Heating K with KOH releases a gas turning universal indicator blue, indicating NH₃ (basic).
• NH₃ evolution from heating with alkali confirms NH₄⁺ presence in J.
• J must contain both Cl⁻ and NH₄⁺, matching NH₄Cl.

Why A is correct:

• NH₄Cl dissociates to NH₄⁺ and Cl⁻; AgNO₃ gives AgCl(s), and heat with KOH yields NH₃(g) via NH₄⁺ + OH⁻ → NH₃ + H₂O.

Why the others are wrong:

• B: Na₂SO₄ lacks Cl⁻, so no AgNO₃ precipitate.
• C: NaCl gives AgCl precipitate but no NH₃ with KOH (no NH₄⁺).
• D: NaOH lacks Cl⁻ and NH₄⁺, so neither test matches.

Final answer: A