Test for Hydrogen & Carbon Dioxide (Edexcel GCSE Chemistry): Revision Note
Exam code: 1CH0
Test for Hydrogen & Carbon Dioxide
Testing Hydrogen
The test for hydrogen consists of holding a burning splint held at the open end of a test tube of gas
If the gas is hydrogen it burns with a loud “squeaky pop” which is the result of the rapid combustion of hydrogen with oxygen to produce water
Be sure not to insert the splint right into the tube, just at the mouth, as the gas needs air to burn
Diagram showing the test for hydrogen gas
Examiner Tips and Tricks
It is easy to confuse the tests for hydrogen and oxygen. Try to remember that a ligHted splint has a H for Hydrogen, while a glOwing splint has an O for Oxygen.
Testing Carbon Dioxide
The test for carbon dioxide involves bubbling the gas through an aqueous solution of calcium hydroxide (limewater)
If the gas is carbon dioxide, the limewater turns milky or cloudy
Diagram showing the test for carbon dioxide gas
Examiner Tips and Tricks
Sometimes students think that extinguishing a burning splint indicates carbon dioxide gas. However, while it is a property of carbon dioxide, other gases, such as nitrogen, will also do this, so the test is not definitive and should not be quoted in an exam answer.
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