Diffusion of Gases: Interactive Experiment
Class IX–X Chemistry | Explore how ammonia and hydrogen chloride gases diffuse and form a white ring.
Learning by observation and simulation!
1. Experiment Setup
Two cotton plugs are soaked separately in aqueous ammonia and hydrochloric acid. They are placed at opposite ends of a long glass tube.
The animation uses coloured dots to distinguish the gases. The actual gases are colourless.
2. Run the Gas Diffusion Simulation
Press Start to observe the motion of the gas particles.
This is a conceptual animation, not a measurement of actual laboratory diffusion time or particle concentration.
3. Step-by-Step Procedure
- Take a long, dry glass tube.
- Soak one cotton plug in aqueous ammonia solution and another in concentrated hydrochloric acid, following an approved laboratory procedure.
- Using suitable laboratory protection, place the plugs at opposite ends of the tube.
- Observe the gases spreading through the tube.
- A white ring of ammonium chloride forms nearer the hydrochloric acid end.
4. Chemical Reaction
NH₃(g) + HCl(g) → NH₄Cl(s)
Ammonia gas reacts with hydrogen chloride gas to form solid ammonium chloride, which appears as a white ring or cloud.
5. Why Does the White Ring Form Near the HCl End?
Ammonia has a lower molar mass than hydrogen chloride. At the same temperature, ammonia molecules have a higher average speed and generally diffuse faster.
- Molar mass of NH₃ = 17 g/mol
- Molar mass of HCl ≈ 36.5 g/mol
- Ammonia travels farther along the tube before the two gases meet.
Therefore, the white ammonium chloride ring forms closer to the HCl end.
Important: Molecular speed and diffusion rate are related, but are not identical. The experiment illustrates the general relationship between molar mass and diffusion under comparable conditions.
6. Test Your Understanding
Select one answer for each question and click Submit Answers.
Conclusion
Diffusion demonstrates the continuous random motion of gas particles. Lighter gases generally diffuse faster than heavier gases under comparable conditions. The ammonia and hydrogen chloride experiment provides visible evidence of diffusion and chemical reaction.
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