Halide Ion Identification via Acid and Precipitation Tests

Steps:

• Q's water solubility and white solid form indicate a soluble ionic salt like NaCl.
• Concentrated H2SO4 on dry Q produces white HCl fumes, characteristic of chloride salts (NaCl + H2SO4 → NaHSO4 + HCl).
• HCl gas reacts with AgNO3 to form white AgCl precipitate (HCl + AgNO3 → AgCl ↓ + HNO3).
• AgCl dissolves in dilute NH3 due to complex formation ([Ag(NH3)2]+), confirming chloride.

Why C is correct:

• NaCl produces HCl gas with H2SO4, yielding AgCl precipitate soluble in dilute ammonia per standard halide test.

Why the others are wrong:

• A. AgCl: Insoluble salt; does not produce fumes with H2SO4.
• B. NaBr: Forms HBr gas, giving pale yellow AgBr precipitate insoluble in dilute NH3.
• D. PbBr: Produces HBr, giving AgBr precipitate insoluble in dilute NH3; PbBr2 has low water solubility.

Final answer: C