What color precipitate forms when iodide ions are tested with acidified dilute nitric acid and silver nitrate?

• A. Yellow precipitate.
• B. White precipitate.
• C. Cream precipitate.
• D. No precipitate.

Answer: (A)

When testing halide ions with silver nitrate in an acidic medium, silver halides form as precipitates, and their colors differ for each halide. Iodide reacts with Ag+ to produce silver iodide, which is very insoluble and appears as a yellow precipitate. The dilute nitric acid acidifies the solution to remove interfering carbonate ions, so the test mainly shows the formation of a silver halide. If chloride were present, you’d get a white precipitate of silver chloride; if bromide, a cream-colored precipitate of silver bromide. The observed yellow precipitate therefore indicates iodide ions.