Testing cations

• How do you carry out a flame test?

  1. Take a platinum wire loop and clean it by
  2. Dipping it in dilute hydrochloric acid
  3. heating it over a Bunsen burner flame
  4. Dip the wire loop in the compound you want to test
  5. Hold it in the blue part of the flame
  6. Observe the colour of the flame
• Colour of each metal's flame:

  • lithium ions - crimson flame
  • Sodium ions - yellow flame
  • Potassium ions - lilac flame
  • Calcium ions - orange-red flame
  • Copper ions - green flame
• Metal hydroxide test:

  React the metal with sodium hydroxide solution and see what colour the solution turns
• Results of the metal hydroxide test:

  • Copper-blue precipitate
  • Calcium - white precipitate
  • Iron (II) - green precipitate
  • Iron (III) - brown precipitate
  • Magnesium - white precipitate
  • Aluminium - forms a white precipitate => dissolves to form a colourless solution with excess sodium hydroxide