chemical tests

• Test for hydrogen


  1. Use a burning splint held at the open end of a test tube of the gas

  2. Creates a 'squeaky pop' sound
• Test for oxygen


  1. Use a glowing splint inserted into a test tube of the gas

  2. Splint relights in oxygen
• Test for carbon dioxide


  1. Bubble the gas through limewater (calcium hydroxide)

  2. Limewater turns milky (cloudy)
• Test for ammonia


  1. Makes damp red litmus paper turn blue

  2. Forms a white smoke of ammonium chloride when hydrogen chloride gas is held near it
• Test for chlorine


  1. Put damp litmus paper into chlorine gas

  2. Litmus paper is bleached and turns white
• Flame test


  1. Take a sample of the metal on a wire and put it in a flame

  2. The flame will turn a specific colour, showing what metal it is
• Cations tested in flame tests


  • Li+
  • Na+
  • K+
  • Ca2+
  • Cu2+
• Lithium gives a red flame
• Sodium gives a yellow flame
• Potassium gives a lilac flame
• Calcium gives an orange-red flame
• Copper gives a blue-green flame
• Test for NH4+ using NaOH(aq)


  1. Ammonia reacts with NaOH(aq) forming NH3(g)

  2. Use damp red litmus paper - it will turn blue showing the presence of ammonia gas
• Test for Cu2+ using NaOH(aq)


  Produces a blue precipitate
• Test for Fe2+ using NaOH(aq)


  Produces a green precipitate
• Test for Fe3+ using NaOH(aq)


  Produces a brown precipitate
• Test for Cl-, Br- and I- using acidified silver nitrate solution


  1. First add dilute nitric acid, followed by silver nitrate solution

  2. Chloride gives a white precipitate

  3. Bromide gives a cream precipitate

  4. Iodide gives a yellow precipitate
• Test for SO42- using acidified barium chloride solution


  1. First add dilute hydrochloric acid, followed by barium chloride solution

  2. A white precipitate will form when sulfate ions are in this solution
• Test for CO32- using hydrochloric acid


  1. Carbonates react with dilute acids to create carbon dioxide

  2. This gas can be bubbled through limewater, if the limewater goes cloudy, the gas is CO2
• Test for water using anhydrous copper(II) sulfate


  1. Anhydrous copper(II) sulfate is white

  2. When water is present, it turns blue
• Test to show if a sample of water is pure

  1. Evaporate the water on an evaporating dish

  2. Measure the boiling point of the water