TESTING FOR CATIONS
- Created by: olivialcock
- Created on: 24-08-16 14:41
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- TESTING FOR CATIONS
- FLAME TESTS
- Potassium (K+) --> lilac flame
- Calcium (Ca2+) --> brick red flame
- Lithium (Li+) --> red flame
- Sodium (Na+) --> orange flame
- How to do a flame test
- 2. Hold the wire in a flame and it should burn with no colour
- 1. Get a wire loop and clean it by dipping it into some dilute hydrochloric acid
- Then you can dip the loop into the sample you want to test and put it back in the flame
- IDENTIFYING METAL CATIONS
- COPPER (II)
- blue precipiate
- Cu2+ + 2OH- ---> CU(OH)2
- IRON (II)
- sludgy green precipitate
- Fe2+ + 2OH- ---> FE(OH)2
- IRON (III)
- Fe3+ + 3OH- ---> FE(OH)3
- red/brown precipitate
- Many metal hydroxides are insoluble and precipitate out of solution when formed
- Some of these hydroxides have a characteristic colour which you can see if you add a few drops of sodium hydroxide solution
- COPPER (II)
- TESTING FOR AMMONIUM IONS
- TEST: add sodium hydroxide to the solid or solution being tested
- RESULT: if ammonium ions are present then a pugnent smelling gas is produced
- The gas produced is called ammonia gas (NH3)
- When ammonia gas is present, it turns damp red litmus paper blue
- The gas produced is called ammonia gas (NH3)
- FLAME TESTS
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