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cation tests
qualitative analysis
Question | Answer |
---|---|
Flame tests Lithium (Li+) | Crimson/red |
Flame tests Sodium (Na+) | Yellow |
Flame tests Potassium (K+) | Lilac |
Flame tests Calcium (Ca2+) | Orange - red |
Flame tests Copper (Cu2+) | Blue - green |
WELL DONE - NOW THE OTHER TESTS FOR CATIONS | |
How do you perform an alternative test for metal cations? | 1) Dissolve salt in water to make a solution. 2) Add a few drops of NaOH solution and observe precipitate colour 3) If precipitate produced is white then add excess NaOH solution and watch to see if the precipitate dissolves |
Alternative ppt test Copper (Cu2+) | Blue ppt |
Alternative ppt test Iron II (Fe2+) | Green ppt |
Alternative ppt test Iron III (Fe3+) | Brown ppt |
Alternative ppt test Aluminium (Al3+) | White ppt Ppt dissolves in excess NaOH solution |
Alternative ppt test Calcium (Ca2+) | White ppt Ppt does NOT dissolve in excess NaOH solution |
What substance do you add to a metal salt solution to form a precipitate during a test for metal cations | Sodium Hydroxide (NaOH) |
Order of tests for cations | Flame test Sodium hydroxide coloured precipitates Testing gasses and ammonium |
Order of tests for anions | Test for carbonate - test for co2 Test for sulfates - white barium sulfate precipitate Test for halide ions - colour of silver halide (cream, white and yellow) |
why do you need to test in order? | If any HCL or BaCl2 is added to test for carbomante or sulfate there will be chloride ions in the solution. These will be tested and provide a false positive result for chloride ions |