Diffusion of gases - Simulation

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.

Observe: Ammonia gas and hydrogen chloride gas diffuse towards each other. Where they meet, a white ring of ammonium chloride forms.

The animation uses coloured dots to distinguish the gases. The actual gases are colourless.

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2. Run the Gas Diffusion Simulation

Ammonia (NH₃) Hydrogen chloride (HCl) Ammonium chloride (NH₄Cl)

Simulation speed: Normal

0 sElapsed simulation time

0%Illustrative progress

ReadySimulation status

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.

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3. Step-by-Step Procedure

1. Take a long, dry glass tube.
2. Soak one cotton plug in aqueous ammonia solution and another in concentrated hydrochloric acid, following an approved laboratory procedure.
3. Using suitable laboratory protection, place the plugs at opposite ends of the tube.
4. Observe the gases spreading through the tube.
5. A white ring of ammonium chloride forms nearer the hydrochloric acid end.

Safety first: Ammonia and hydrochloric acid fumes are irritating and hazardous. This demonstration must be performed by a trained teacher in a suitable fume hood, with appropriate PPE. Never smell the gases directly. Students can use this simulation instead of handling the chemicals.

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.

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6. Test Your Understanding

Select one answer for each question and click Submit Answers.

1. What is diffusion? Conversion of a solid into a liquid Movement of particles from a region of higher concentration to lower concentration due to random motion Only the movement of liquids

2. What is the formula of ammonia? NH₃ HCl NH₄Cl

3. What is the white substance formed in the tube? Sodium chloride Ammonia Ammonium chloride

4. Why does the ring form nearer the HCl end? HCl diffuses faster than ammonia Ammonia generally diffuses faster than HCl The gases do not move

5. Which gas has the lower molar mass? HCl Both have equal molar masses NH₃

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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