11.3.2—Reactions of halide ions

Aqueous halide ions form precipitates with silver ions: Ag⁺ + X⁻ → AgX. The precipitate colour and its response to aqueous ammonia provide a structured identification test.

Chloride, bromide and iodide give different AgX observations. Concentrated sulfuric acid gives a second line of evidence: halide ions reduce sulfuric acid to different extents, so balanced equations and oxidation states matter.

Add nitric acid then silver nitrate to an unknown. A pale precipitate that dissolves in dilute ammonia is consistent with AgCl; use the whole observation sequence rather than colour alone.

Ammonia is not just a washing step, and precipitate colour alone is not a complete identification. Keep test conditions and ionic equations explicit.