3.1.4 Testing for ions (not halides) Flashcards
1
Q
How do you test for carbonate ions and what is the result
A
- Add and acid
- fizzes
- collect gas
- bubble through limewater if it was a carbonate the limewater will turn cloudy as it is in the presence of carbon dioxide.
2
Q
How do you test for sulfate ions and what are the results
A
- Add Ba2+ ions ( eg. Barium chloride) and a few drops of dilute HCl
- a white precipitate forms
3
Q
How do you test for ammonium ions and what are the results
A
- add sodium hydroxide
- produces aqueous ammonia
- heat to produce NH3 gas
- test with damp litmus paper
- will turn blue if the ions are present.
4
Q
what order should ion tests be carried out in
A
Carbonate - sulfate - halide - ammonium
5
Q
why should anions be tested in the carbonate-sulfate-halide order
ammonium is a cation
A
to prevent false positives - Barium carbonate and silver sulfate also produce white precipitate and so sufates must be tested for before halides and carbonate before sulfates.
