TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > Edexcel Chemistry Unit 3B - Laboratory Techniques - Test for Gases
Test for Gases.
Specification
b) Recognise the chemical tests for simple gases, to include hydrogen, oxygen, carbon dioxide, ammonia, chlorine, nitrogen dioxide and sulphur dioxide
Tests
| Name
| Formula
| Test
| Observations
|
| Hydrogen
| H2
| Ignite gas.
| Squeaky pop is heard.
|
| Oxygen
| O2
| Place a glowing splint in a sample of the gas.
| The glowing splint relights.
|
| Carbon dioxide
| CO2
| Bubble gas through limewater (saturated solution of calcium hydroxide)
| A solution turns from colourless to cloudy. A white (milky) precipitate of calcium carbonate forms which is sparingly soluble.
|
| Ammonia
| NH3
| Test for gas using damp red litmus paper.
| Litmus paper turns blue.
|
| Chlorine
| Cl2
| Test 1
Test for gas using damp litmus paper (red or blue)
| Chlorine bleaches the litmus paper very quickly.
|
Test 2
Test for gas using moist starch-iodide paper.
| The paper turns blue-black.
|
Test 3
Pass gas through a solution of a bromide.
| The solution turns from colourless to orange.
|
Test 4
Pass gas through a solution of an iodide.
| The solution turns from colourless to brown (possibly with a black precipitate, iodine).
|
| Nitrogen dioxide
| NO2
| Not many tests for this gas.
| The gas is brown.
|
| Sulphur dioxide
| SO2
| Test 1
Bubble gas through a solution of potassium dichromate (VI) dissolved in sulphuric acid.
| The solution turns from orange to green.
|
Test 2
Bubble gas through a solution of potassium manganate (VII) dissolved in sulphuric acid.
| The solution turns from purple to colourless.
|
Also See
Why not read these other revision notes for Edexcel Unit 3B - Laboratory Techniques?
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