Testing for cations

• What are the two groups of tests for cations?

  Flame tests and metal hydroxide tests
• How do flame tests help identify metal ions?

  By observing the color of the flame produced
• What are the steps to perform a flame test?

  1. Clean wire loop with hydrochloric acid and distilled water.
  2. Heat the wire loop over a Bunsen burner flame.
  3. Dip the wire loop into the compound to test.
  4. Hold the loop in the blue part of the flame.
  5. Observe the flame color as the compound burns.
• What does the term 'cation' refer to?

  A positively charged ion
• Give an example of a cation.

  Mg$^{2+}$
• Why are most cations metals?

  Because metals form positive ions
• What is the exception to the rule that cations are metals?

  The ammonium ion, NH$_{4}^{+}$
• What happens when cations react with sodium hydroxide?

  They form metal hydroxides
• What color flame do lithium ions (Li$^{+}$) produce?


  Crimson flame
• What color flame do sodium ions (Na$^{+}$) produce?


  Yellow flame
• What color flame do potassium ions (K$^{+}$) produce?


  Lilac flame
• What color flame do calcium ions (Ca$^{2+}$) produce?


  Orange-red flame
• What color flame do copper ions (Cu$^{2+}$) produce?


  Green flame
• What are the key steps in preparing for a flame test?

  • Clean the wire loop with hydrochloric acid.
  • Rinse the loop in distilled water.
  • Heat the loop over a Bunsen burner flame.
• What are the colors produced by different metal ions during flame tests?

  • Lithium: Crimson
  • Sodium: Yellow
  • Potassium: Lilac
  • Calcium: Orange-red
  • Copper: Green