Chemistry Unit 3 Chemical Tests

Cards to help you learn the chemical tests for Unit 3 AQA

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  • Created by: Rachael
  • Created on: 21-05-11 13:51

Flame Tests

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

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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

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Ammonia

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.

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Carbonates

  • 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.
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Sulphates

  • 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!
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Halides

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.
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Nitrates

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.
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Other tests

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.
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Comments

Jennifer Ullah

OH GOOD LORD!!! Thank you so much :) I now have something to help me remember these :D

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