Separate Chemistry 2 - Ion tests Flashcards
Which tests test for metal ions?
- Flame test
- Hydroxide tests
What is the method for a flame test?
1) Clean the flame loop in acid
2) Place sample onto the loop
3) Place loop at the side of a roaring blue flame
4) Witness colour change
What are the results of different metals in a flame test?
Potassium (K+) --> Lilac flame Lithium (Li+) --> Red flame Sodium (Na+) --> Yellow flame Calcium (Ca2+) --> Orange flame Copper (Cu2+) --> Blue-green flame
How does a flame test work?
Excitation of outer electrons.
What is the method for a hydroxide test?
1) Dissolve the solid salt in distilled water
2) Add a few drops of sodium hydroxide
3) Record the colour of the precipitate
What are the results of different metals in a hydroxide test?
Iron II (Fe2+) --> Green Iron III (Fe3+) --> Brown Copper (Fe3+) --> Blue Calcium (Ca2+) --> White Aluminium (Al3+) --> White (dissolves with excess NaOH
How does the hydroxide test work?
Displacement reaction - sodium is more reactive and bonds to the hydroxide ions, leaving the metal precipitate.
What does the halide test, test for?
Halide ions.
Which tests test for non-metal ions?
- Halide test
- Carbonate test
- Sulphate test
- Ammonium test
What is the method for a halide test?
1) Dissolve the salt in distilled water
2) Add a few drops of nitric acid
3) Add a few drops of silver nitrate
4) Record the colour of the precipitate
What are the results of the different ions in a halide test?
Chloride (Cl-) –> White
Bromide (Br-) –> Cream
Iodine (I-) –> Yellow
How does a halide test work?
The silver reacts with the halide to form insoluble silver halides.
What is the method for a carbonate test?
1) Dissolve the solid in a few drops of acid
2) Observe for bubbles (gas production)
3) Bubble gas through limewater
What is the result of a carbonate test?
If carbon dioxide is being produced, the limewater will go cloudy.
What is the method for a sulphate test?
1) Dissolve the solid in distilled water
2) Add a few drops of hydrochloric acid
3) Add a few drops of barium chloride
What is the result of a sulphate test?
A white precipitate forms (insoluble barium sulphate).
How does a sulphate test work?
The acid removes carbonate ions that might produce a false test.
Insoluble barium sulphate forms if sulphate is present.
What is the method for an ammonium test?
1) Dissolve the solid salt in distilled water
2) Add sodium hydroxide and warm gently
3) Place damp red litmus paper in the test tube and observe
What is the result of an ammonium test?
Red litmus paper will turn blue.
What are three instrumental methods of detecting and analysing substances?
- Mass spectrometry
- Infrared spectroscopy
- Gas chromatography
How does mass spectrometry work?
It measures Mr values and identifies compounds.
How does infrared spectroscopy work?
It detects covalent bonds and identifies compounds
How does gas chromatography work?
It measures the amounts of each component in a mixture.
What do instrumental tests offer?
Improved:
- Sensitivity
- Accuracy
- Speed
