chemical tests

• Hydrogen


  • A lit splint will burn with a squeaky pop
• Oxygen


  • A glowing splint will re-light
• Carbon dioxide


  • Turns limewater cloudy
• Ammonia


  • Turns damp red litmus paper blue
• Chlorine


  • Turns damp blue litmus paper red before bleaching it white
• Flame tests


  1. Clean a platinum wire loop by dipping it in dilute HCl then hold it under a flame

  2. It won't burn with any colour, then dip it into the sample you want to test

  3. Put it back in the flame (the hottest bit)
• Cation tests


  1. Use sodium hydroxide

  2. Observe colour for metal ions: Copper(II)-blue, Iron(II)-green, Iron(III)-red-brown, Ammonium-ammonia gas given off
• Anion tests


  1. Halides (Br, I-) with nitric acid + silver nitrate: Chloride-white precipitate, Bromide-cream precipitate, Iodide-yellow precipitate

  2. Test for sulfate with acidified barium chloride: produces a white precipitate
• Carbonate tests


  Fizzes with hydrochloric acid, giving off CO2 which can be tested using limewater
• Anhydrous copper(II) sulfate


  • Turns blue when water is added, forming blue crystals from white powder
• Pure water will always: boil at 100°C, freeze at 0°C