Qualitative analysis: tests for ions Flashcards
1
Q
Why must the test for any ion be unique?
A
Wouldn’t be able to know what ion it was if more than one gave the same result innit
2
Q
how to do a flame test?
A
- Light bunsen burner to non-safety flame
- Take a wire loop, dip it into hydrochloric acid, rinse in distilled water and hold it over a flame. It should produce no colour if it is clean.
- Dip the wire loop into the metal
- Hold it above the fire and use the colour to determine the ion
3
Q
How to do a precipitation test?
A
- Add sodium hydroxide solution to the compound
- If a hydroxide precipitate forms, you can use the colour to tell which metal ion was there
4
Q
How to do halide test?
A
- add dilute nitric acid
- add silver nitrate solution
- nitric acid gets rid of carbonate ions because they confuse results
5
Q
how to test for carbonate ions
A
- Add dilute acids, mixture will fizz
- carbonate reacts with acid to form carbon dioxide and water
- Check gas produced is carbon dioxide by bubbling through limewater
6
Q
How to test for sulfate ions
A
- add hydrochloric acid, stops any other precipitation reactions
- Add barium chloride
- If there are sulphate ions, white precipitate of barium sulphate forms
7
Q
lithium result
A
red flame
8
Q
sodium result
A
yellow flame
9
Q
potassium result
A
lilac flame
10
Q
calcium test results
A
- orange-red flame
- White precipitate
11
Q
copper test results
A
- blue-green flame
- blue precipitate
12
Q
aluminium test results
A
precipitate: white at first. However, will dissolve and turn colourless when you add excess sodium hydroxide
13
Q
Iron II results
A
Precipitate: Green
14
Q
Iron III results
A
Precipitate: Brown
15
Q
test for ammonium ions/ammonia
A
- Add sodium hydroxide
- Heat gently
- Place damp red litmus paper over it
- if it is ammonia, will turn blue
16
Q
chloride test results
A
- white precipitate silver chloride
17
Q
bromide test results
A
- cream precipitate silver bromide
18
Q
iodide test results
A
- yellow precipitate silver iodide
19
Q
How can you use instrumental methods of analysis?
A
- Flame photometry uses photometer
- Analyses spectra produced by ions
- Sensitive, fast and accurate
