Testing for Ammonia
- Ammonia is a gas with a pungent smell that turns damp red litmus paper blue
- Hold the litmus paper near the mouth of the test tube, but be careful to avoid touch the sides of the test tube
- If you are testing for ammonia produced from ammonium ions and sodium hydroxide, avoiding touching the sides prevents traces of sodium hydroxide from also turning the red litmus paper blue
Diagram showing how to perform the test for ammonia gas using damp red litmus paper
- Another test for ammonia is to react the gas with HCl
- A white smoke of ammonium chloride is formed if ammonia gas is present:
NH3 + HCl → NH4Cl
Exam Tip
Make sure you understand the difference between ammonium and ammonia. Ammonium refers to the aqueous cation, NH4+, whereas ammonia is the gas, NH3.
