- Created by: Punam
- Created on: 10-05-12 09:19
Flame tests: Put compound in a platinum wire loop dipped in hydrochloric acid, and put it over a blue bunsen flame.
Calcium gives a BRICK RED flame
Lithium gives a BRIGHT RED flame
Sodium gives a GOLDEN flame
Barium gives a GREEN flame
Potassium gives a LILAC flame
Tests for Positive Ions
Put unknown substance in Sodium Hydroxide (NaOH) solution.
Aluminium, Calcium, and Magnesium ions form White Percipitate. To find out which one specifically, add more NaOH--aluminium ions dissolve in it eventually. If it doesn't dissolve its either calcium or magnesium. To find out if its calcium or magnesium, we can do flame tests (Ca--brick red flame, Mg--no particular colour)
Copper (II) ions form light blue percipitate
Iron (II) forms a dirty green percipitate
Iron (III) forms a reddish-brown percipitate
Ammonium ions react with NaOH to form ammonia and water. When ammonia and water is forms, we can heat up solution and test the gas given off with damp red litmus paper (which would turn blue).
Tests for Negative Ions
Carbonates: add HCL to substance, if it fizzes it gives out CO2 gas. Pump gas into limewater--if it turns milky, then its CO2.
Halides: add dilute nitric acid and silver nitrate solution to the substance...
- Chloride ions form a WHITE PERCIPITATE
- Bromide ions form a CREAM PERCIPITATE
- Iodine ions form a PALE YELLOPW PERCIPITATE
Sulphates: add HCL and barium chloride solution. If sulphate ions are present then a white percipitate is formed.
Nitrate: Test for ammonia is used again here. Add NaOH to unknown substance and warm it. If no ammonia is detected, add aluminium powder, so nitrate ions turn into ammonia so can be detected.