Tests for Ions

• test for carbonates


  add dilute hydrochloric acid

  carbonates present will form carbon dioxide so will fizz

  test for carbon dioxide produced by bubbling it through limewater
• test for sulfates


  add hydrochloric acid to remove any carbonates so no false results

  cadd barium chloride solution

  if sulfate is present a white precipitate of barium sulfate forms

  Ba2+ +SO42- → BaSO4
• test for ammonia gas

  damp red litmus paper turns blue

  ammonia is alkaline
• test for ammonium ions

  add sodium hydroxide

  heat gently

  test for ammonia gas as if there's ammonium ions present ammonia gas is produced

  NH4+ + OH- → NH3 + H2O

  do it in fume cupboard as it produces irritant
• test for hydroxides


  turn red litmus paper blue because they're alkaline

  but it doesn't mean hydroxides are present because any alkali can turn litmus paper blue

  More tests needed - eg: spectroscopy