GCSE Chemistry (AQA)

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Testing for Anions

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Chemical analysis Identification of ions by chemical and spectroscopic means

Testing for Anions

5:21 Tests for Ions
Spec 4.8.3.3 4.8.3.4 4.8.3.5
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  • Chemical tests can identify specific ions in a solution.
  • An ion is a negatively charged particle formed by an atom gaining electrons.
  • Examples of ions include carbonate ions (C3 two minus), halide ions (CL minus), and sulfate ions (SO four two minus).
  • Carbonate ions can be detected by adding a dilute acid, such as hydrochloric acid, to the sample.
  • If carbonate ions are present, CO2 bubbles will be produced, which can be identified using lime water that turns cloudy.
  • Halide ions can be detected by adding dilute nitric acid followed by silver nitrate.
  • Halide ions include chloride (CL minus), bromide (BR minus), and iodide (I minus).
  • Silver chloride forms a white precipitate, silver bromide forms a cream precipitate, and silver iodide forms a yellow precipitate.
  • Sulfate ions can be detected by adding dilute hydrochloric acid and barium chloride solution.
  • If sulfate ions are present, a white precipitate will form.
  • The tests and results for these ions are important for exams.

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