Identification via ammonium and chloride ion tests

Steps:

• Observe white crystalline solid: all options fit, so proceed to confirmatory tests.
• Test for ammonium: heat with NaOH; ammonia gas (smoky NH4Cl fumes or Nessler's reagent positive) confirms NH4+ ion.
• Test for chloride: add AgNO3; white precipitate forms, soluble in dilute NH3, confirming Cl- over Br-.
• Rule out aluminium salts: no amphoteric behavior or alizarin red S test for Al3+.

Why D is correct:

• Ammonium chloride (NH4Cl) produces ammonia gas with bases (due to NH4+ hydrolysis) and gives a white AgCl precipitate soluble in NH3 (Cl- ion characteristic).

Why the others are wrong:

• A: Aluminium bromide lacks NH4+ (no ammonia gas) and gives pale yellow AgBr insoluble in dilute NH3.
• B: Aluminium chloride lacks NH4+ (no ammonia) and shows Al3+ amphoteric properties, not matching ammonium tests.
• C: Ammonium bromide produces ammonia but gives pale yellow AgBr precipitate insoluble in dilute NH3.

Final answer: D