Tests for Ions

• Group 2 flame tests

  • calcium (Ca2+) - brick red
  • strontium (Sr2+) - red
  • barium (Ba2+) - pale green
• Ammonia gas (NH3) is alkaline so can be tested with damp red litmus paper
• Test for ammonium (NH4+) ions1

  1. add sodium hydroxide solution - hydroxide ions will react with the ammonium ions to make ammonia gas
  2. heat gently
  3. damp red litmus paper turns blue
• Test for sulphate ions (SO4,2-)

  1. add dilute hydrochloric acid
  2. add barium chloride solution (BaCl2)
  3. forms white precipitate
• test for hydroxide ions

  1. use pH indicator eg: red litmus turns blue
• test for halide ions

  1. add dilute nitric acid
  2. add silver nitrate solution
  3. chlorine = white precipitate, bromine = cream precipitate, iodine = yellow precipitate
  4. add dilute ammonia solution to tell apart
• test for carbonate ions (CO3,2-)

  1. add dilute hydrochloric acid
  2. limewater turns cloudy