Halide identification via silver precipitates and ammonia solubility

Steps:

• Silver nitrate forms precipitates with halides: AgCl (white), AgBr (pale yellow), AgI (yellow).
• Pale yellow initial precipitate suggests a mixture of white AgCl and yellow AgI, appearing pale overall.
• Concentrated ammonia dissolves AgCl completely but leaves AgI insoluble.
• Resulting darker yellow precipitate confirms undissolved AgI from sodium chloride and iodide.

Why D is correct:

• NaCl and NaI yield AgCl + AgI (pale yellow mix); ammonia dissolves AgCl per [Ag(NH₃)₂]⁺ formation, leaving yellow AgI.

Why the others are wrong:

• A: NaBr yields pale yellow AgBr, which fully dissolves in ammonia, leaving no precipitate.
• B: NaCl + NaBr yields pale mix that fully dissolves in ammonia.
• C: NaI yields yellow AgI, which remains unchanged and does not dissolve.

Final answer: D