C3 Topic 1
- Created by: ldupre03
- Created on: 24-04-17 16:57
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- Water Testing
- Qualitative and Quantitative testing
- Qualitative analysis investigates the types substance present in a sample.
- Quantitative analysis measures the amount of each substance present in a sample.
- The test for a particular ion should be unique. It must give a positive result with only one type of ion. This way you can be sure which ions are present in a sample.
- Flame tests
- Used to detect some metal cations
- Sodium= yellow
- Potassium= lilac
- Calcium= red
- copper= green/blue
- Used to detect some metal cations
- Hydroxide precipitates
- How do you carry out tests for metal cations using sodium hydroxide solution?
- 1) dissolve the sample in water
- 2) Then add a few drops of sodium hydroxide solution.
- (Many metal cations in solutions form insoluble precipitates when this is done)
- 1) dissolve the sample in water
- Aluminium and calcium ions both produce a white precipitate
- the calcium hydroxide precipitates does not redissolve
- the Aluminium hydroxide precipitates redissolves to form a colourless solution when excess sodium hydroxide solution is added.
- must know the colours for these hydroxide precipitates:
- calcium= white
- Iron (III)= brown
- aluminium= white
- copper= pale blue
- iron(II)= green
- How do you carry out tests for metal cations using sodium hydroxide solution?
- Calcium ions and copper (II) ions are detected using flame tests or hydroxide precipitate tests
- Sodium ions and potassium ions are detected using flame tests
- Qualitative and Quantitative testing
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