Testing for hydrogen: a lit splint gives a squeaky pop
Definition
Hydrogen
A gaseous element that burns rapidly with a pop sound when tested with a burning splint.
Definition
Burning splint
A thin wooden splint that has been lit and still has a flame.
- Collect the gas in a test tube and hold a lit (burning) splint at the open end.
- Hydrogen burns very quickly and you hear a squeaky pop.
- The pop is a small explosion as hydrogen reacts with oxygen from the air: 2H2+O2→2H2O2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}2H2+O2→2H2O.
- The only product is water, so the sound is the sign, not any colour change.
Exam technique
- Name both the test and the result: a lit splint and a squeaky pop.
- A squeaky pop on its own is enough to identify the gas as hydrogen.
Why it works and where students slip
- Hydrogen is flammable, so it ignites in the flame of the splint.
- Use a burning splint, not a glowing one, because a glowing splint tests for oxygen.
- Keep the volume small, since larger amounts of hydrogen and air burn more violently.
Self review
- What do you use to test for hydrogen?
- What do you observe if hydrogen is present?
- Write the equation for hydrogen burning in oxygen.
- Why must the splint be burning rather than glowing?
