HydrogenOxford AQA IGCSE Chemistry: Revision notes
Section 1
What is the test for hydrogen gas?
The test for hydrogen gas is to hold a lighted splint at the mouth of a test tube containing the gas. If hydrogen is present, it burns rapidly with a distinctive squeaky pop.
This is one of the standard gas tests used in chemical analysis to identify an unknown gas produced in a reaction.
Section 2
How is the test carried out?
- Collect a sample of the gas to be tested in a test tube (e.g. by collection over water or upward delivery from a reaction).
- Light a wooden splint.
- Bring the lighted splint quickly to the open mouth of the test tube.
- Listen for the result: a squeaky pop confirms hydrogen is present.
In an exam answer, describe both the action (lighted splint held at the mouth of the tube) and the observation (squeaky pop) - a mark is usually given for each.
Section 3
Why does hydrogen produce a squeaky pop?
Hydrogen gas reacts explosively with oxygen in the air when ignited, burning very rapidly: 2H2 + O2 -> 2H2O.
This rapid combustion of a small volume of gas causes the short, sharp sound known as the squeaky pop, and produces water as the only product.
Do not confuse hydrogen's squeaky pop with the test for oxygen, which relights a glowing splint rather than igniting a lit one with a pop.
Must Know
- The test for hydrogen gas: hold a lighted splint at the mouth of the test tube
- A positive result is a squeaky pop
- The squeaky pop happens because hydrogen burns rapidly with oxygen in the air
- The reaction produces only water: 2H2 + O2 -> 2H2O
- This is a standard identification test used in chemical analysis
That's the notes covered.
Carry on to the next subtopic.