When you heat some metals, they burn with a distinctive colour flame.
LITHIUM - burns crimson-red
SODIUM - burns yellow-orange
POTASSIUM - burns lilac
CALCIUM -burns brick-red
BARIUM - burns green
Adding Sodium Hydroxide
If you add a few drops of sodium hydroxide to a solution of any of the following metals, a coloured precipitate will form.
CALCIUM - WHITE
COPPER (II) - BLUE
IRON (II) - SLUDGY GREEN
IRON (III) - REDDISH BROWN
ALUMINIUM - WHITE AND THEN TURNS COLOURLESS
MAGNESIUM - WHITE
There are 3 ways to detect ammonia:
1) It smells similar to cat wee. It is very distinctive.
2) Ammonia turns damp red litmus paper blue.
3) If you add sodium hydroxide to a solution that contains ammonia ions, ammonia is given off.
- To test for Carbon dioxide. you bubble it through limewater and if carbon dioxide is present, the limewater will turn cloudy.
- You can add dilute acid to a carbonate and test to see if carbon dioxide is released.
- If you heat some carbonates, they change colour:
- Copper carbonate turns from green to black and it stays black when cool.
- Zinc carbonate will turn from white to yellow, but will return to white when it cools.
- To test for a sulphate ion, you add dilute HCl and barium chloride solution.
- A white precipitate of barium sulphate forming tells you that the original solutions was a sulphate!
To test for chloride, bromide or iodide ions, add dilute nitric acid and silver nitrate solution.
- A chloride gives a white precipitate.
- A bromide gives a cream precipitate.
- a iodide gives a yellow precipitate.
To identify NITRATES....
- Mix solution with aluminium powder.
- Add sodium hydroxide and heat.
- Nitrate will be reduced to ammonia.
- Test for ammonia with damp red litmus paper, which will turn blue.
Other things to note are...
- Organic compounds burn when heated.
- Compounds with C=C bonds decolourise Bromine water.
- You'll need to find the empirical formula of an organic compound.