White Fumes Mystery
Identify HCl using ammonia gas
What this lesson covers
Why it matters
Two invisible gases meet between two gas jars, and suddenly a thick white fog appears out of nowhere.
The idea in plain words
Observe the equation: NH₃ + HCl → NH₄Cl. Note that two gases combine to form one solid.
Predict first
What is the white solid formed when ammonia and hydrogen chloride gases mix?
The white fumes are solid ammonium chloride, formed by the direct combination of the two gases.
- Ammonium chloride — correct
- Water vapour
- Hydrogen gas
- Chlorine gas
What you do
Bring the mouth of the ammonia gas jar near the hydrogen chloride gas jar. Watch the dense white fumes form.
Check yourself
This reaction is an example of which type?
Two reactants (NH₃ and HCl) combine to form a single product (NH₄Cl).
Why do we see 'white fumes' instead of a gas?
Ammonium chloride is a solid at room temperature; the 'fumes' are fine solid particles.
Which is the simplest balanced equation for this reaction?
The balanced equation is NH₃ + HCl → NH₄Cl.
- Decomposition
- Combination — correct
- Displacement
- The product is a solid suspended in air — correct
- The product is a white gas
- The product is a liquid mist
- NH₃ + HCl → NH₄Cl — correct
- NH₃ + HCl → NH₃Cl + H₂
- 2NH₃ + 2HCl → 2NH₄Cl