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GCSE Chemistry Revision
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GCSE Chemistry revision
Halides
Identification of ions by chemical and spectroscopic means (chemistry only)
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Testing for Halide Ions — Step 1: Removing Impurities
- Dilute nitric acid (not hydrochloric acid) is added first to remove carbonate and sulfite impurities from the sample.
- Hydrochloric acid cannot be used here because it would introduce chloride ions, which would interfere with the halide test.
Testing for Halide Ions — Step 2: The Silver Nitrate Test
- Silver nitrate solution is added to the acidified sample, and the silver ions (Ag⁺) react with any halide ions present to form a coloured precipitate.
- A white precipitate of silver chloride (AgCl) indicates the presence of chloride ions.
- A cream precipitate of silver bromide (AgBr) indicates the presence of bromide ions.
- A yellow precipitate of silver iodide (AgI) indicates the presence of iodide ions.