8.3 Qualitative Analysis

• Test for carbonate ions

  • add dilute nitric acid to sample
  • if bubbles observed, bubble the gas through limewater
  • if limewater turns cloudy, gas is carbon dioxide
• Test for sulfate ions

  • add aqueous barium chloride or barium nitrate
  • white precipitate forms
• Test for halide ions

  • add aqueous silver nitrate
  • precipitate forms
  • white = chloride
  • cream = bromide
  • yellow = iodide
• Test must be carried out in particular order

  • carbonate -> sulfate -> halide
  • carbonate ions produce a precipitate in sulfate and halide tests
  • sulfate ions produce a precipitate in halide test
• Test for ammonium ions

  • add sodium hydroxide to solution and warm mixture
  • test for any gas with damp red litmus paper
  • positive result = litmus paper turns blue
• Silver chloride is soluble in dilute ammonia not concentrated ammonia
• Silver bromide is soluble in concentrated ammonia not dilute ammonia
• Silver iodide is not soluble in dilute or concentrated ammonia