Tests for cations

• How do you identify metal ions

  Flame tests
• lithium ions

  crimson flame
• sodium ions

  yellow flame
• potassium ions

  lilac flame
• calcium ions

  orange-red flame
• copper ions

  green flame
• what precipitate do calcium ions form

  white
• what precipitate do copper ins form

  blue
• what precipitate do Fe2+ ions form

  Green
• what precipitate do Fe3+ ions form

  brown
• what precipitate do aluminium ions form

  white at first

  then it redisolves to form a colourless solution
• how do you do flame tests

  clean a platinum wire loop

  dip the loop into the sample and put it in the flame

  record the colour of the flame
• how do you clean the platinum wire loop

  dip it in dilute HCL and hold it in the blue flame of a Bunsen burner until it burns without any colour
• why can’t you test a sample with a mix of metal ions

  the flame colours of some ions may be hidden by the other colours
• how do you test a compound for metal ions

  add sodium hydroxide solution to form an insoluble hydroxide