Ammonia (Oxford AQA IGCSE Chemistry)
Revision Note
Author
Alexandra BrennanExpertise
Chemistry
Test for Ammonia
Ammonia is a gas with a characteristic sharp choking smell that turns damp red litmus paper blue
Hold the litmus paper near the mouth of the test tube, but be careful to avoid touching the sides of the test tube
If you are testing for ammonia produced from ammonium ions and sodium hydroxide, avoiding touching the sides to prevent traces of sodium hydroxide from also turning the red litmus paper blue
Test for ammonia gas
Another test for ammonia is to react the gas with hydrogen chloride gas from concentrated hydrochloric acid
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.
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