Tests For Chemicals

Tests For Chemicals

1. Gases

   • Chlorine
     • Bleaches damp litmus paper (Turns white)
   • Oxygen
     • Relights a glowing splint
   • Carbon Dioxide
     • Turns lime water milky white
   • Hydrogen
     • Burns with a 'squeaky' pop
   • Ammonia
     • Turns damp RED litmus paper blue

2. Water

   • White Anhydrous Copper(II) Sulphate Powder
     • Turns blue in presence of water
     • BUT does not show if it is pure or not
   • Pure water has specific physical properties that can be tested
     • Boiling point:
       • 100ºC
     • Melting point:
       • 0ºC

3. Cations

   • Flame Tests For Metal Ions
     • Li+ Lithium:
       • Red Flame
     • Na+ Sodium:
       • Yellow Orange Flame
     • K+ Potassium:
       • Lilac Flame
     • Ca2+ Calcium:
       • Orange/Brick-Red Flame
   • NaOH Precipitates
     • Copper(II) Cu2+
       • Blue
     • Iron(II) Fe2+
       • Sludgy Green
     • Iron(III) Fe3+
       • Reddish Brown
     • Many Metal Hydroxides form precipitates when added to Sodium Hydroxide as they are insoluble. The precipitate may have a distinctive colour
   • Ammonium Compounds
     • Add NaOH (Sodium Hydroxide)
       • Test For Ammonia
         • Damp litmus paper bleeches

4. Anions

   • Carbonates
     • Add HCl to sample
       • If Carbonate ions present CO2 will be given off
         • This can be tested in lime water
   • Sulphates
     • Add HCL to remove impurities
       • Then Add Barium Chloride
         • If Sulphate present a white precipitate will form
   • Halides
     • Iodide = Yellow
     • Bromide = Cream
     • Add Nitric Acid to the sample to remove impurities
       • Then add Silver Nitrate Solution
         • See colour of precipitate
     • Chloride = White