Free interactive chemistry · SIM-STATE-002
Diffusion
NH₃ and HCl gases diffuse towards each other along a tube and meet to form a white ring of NH₄Cl.
Open the interactive simulation →How to use this simulation
- Watch the blue NH₃ and green HCl molecules zig-zag along the tube.
- Wait for the white ring to form where they meet.
- Read the meeting point and Graham’s-law numbers in the “Graham” panel.
- Press “Restart” to run it again.
What to notice
- Lighter molecules move faster: rate ∝ 1/√M, so the ring forms nearer the HCl end.
- Molecules collide constantly, so diffusion is much slower than their actual speed.
Try this
Use Graham’s law to predict where the ring forms, then check the value shown.
Try it for free →