Chemistry IGCSE

Chemistry IGCSE

1. Li - Crimson Red flame

2. Na - Yellow-Orange flame

3. K - Lilac Flame

4. Ca - Brick-Red flame

5. Dip clear platinum loop in HCL (aq)

6. Hold in a roaring blue flame

7. Wait till it burns with no colour

8. Dip in sample then place in flame

9. Test for coloured precipitate with Sodium Hydroxide (NaOH)

   • Copper 2+ Ions - Blue precipitate
     • Cu 2+ (aq) + 2OH- (aq) → Cu(OH)2 (s)
   • Iron 3+ ions - Reddish-Brown precipitate
     • Fe 3+ (aq) + 3OH- (aq) → Fe(OH)3 (s)
   • Iron 2+ ions - Sludgy green precipitate
     • Fe 2+ (aq) + 2OH- (aq) → Fe(OH)3 (s)

10. Ammonium Compound + NaOH = Ammonia!

    • Usually smells of cat urine
      • Check using litmus paper
        • Damp red litmus paper blue
          • NH4 give off ions which react with the litmus paper making it blue as it is an alkaline

11. Test for Anions

    • Test for Carbonates
      • Add dilute Hydrochloric acid (aq) to the test sample
        • If carbonates are present then carbon dioxide will be released
          • Carbon dioxide turns limewater cloudy (Test)
            • CO3 (s) + 2H (aq) → CO2 (g) + H2O (l)
    • Test for Sulfates
      • Add dilute Hydrocholoric acid (aq) then barium chloride solution
        • A white precipitate means the compound was origanally a sulfate
          • Ba (aq) + SO (aq) → BaSO4 (S)
    • Test for Halides
      • To test for chloride, bromide or iodide ions, add dilute nitric acid (aq) then add silver nitrate solution (AgNO3)
        • Chloride Ion gives a White Precipitate of Silver Chloride
          • Bromide ion gives a Cream precipitate of Silver Bromide
            • Iodide ion gives a Yellow Precipitate of Silver Iodide
              • Ag (aq) + I (aq) → AgI (S)
            • Ag (aq) + Br (aq) → AgBr (S)
          • Ag (aq) + Cl (aq) → AgCl (S)

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