Tests for ions Flashcards
(11 cards)
1
Q
How do you test for carbonate ions (CO3 -2)?
A
- add a dilute HCL to the solution
- Collect any gas formed and pass it through limewater
2
Q
What is a positive result for a carbonate ion test?
A
- colourless gass produces
- gas turns limewater cloudy
3
Q
How do you test for sulfate ions (SO4 -2)?
A
- add dilute hydrochloric acid to acidify sample
- add barium chloride to the solution
4
Q
What is a positive result for a sulfate ion test?
A
- white precipitate of barium sulfate is produced
5
Q
How do you test for halide ions (Cl, Br, I)?
A
- dissolve solution in nitric acid
- add silver nitrate
- note the colour of precipitate formed
- add dilute ammonia if colour is hard to tell
- then add concentrated ammonia
- note solubility of the precipitate in ammonia
6
Q
What is a positive result for a halide ion test?
A
- silver chloride - white precipitate + soluble in dilute ammonia
- silver bromide - cream precipitate + soluble in conc. ammonia
- silver iodide - yellow precipitate + insoluble in ammonia
7
Q
Why do you dissolve a test for halide ions in nitric acid first?
A
Prevent false positive from carbonate ions which would precipitate with silver
8
Q
How do you test for ammonium ions (NH4+)?
A
- add warm sodium hydroxide solution to the solution
- ammonia gas should be produced
- test any gas produced with red litmus paper
9
Q
What is a positive result for an ammonium ion test?
A
- ammonia gas will turn litmus paper blue
- ammonia gas has a distinctive smell
10
Q
What colour do the halogens form in water?
A
- Cl2 = pale green
- Br2 = orange
- I2 = brown
11
Q
What colour do halogens form in a non polar solvent (cyclohexane)?
A
- Cl2 = pale green
- Br2 = orange
- I2 = violet
