Diffusion of nitrogen dioxide into air

Demonstration

Apparatus and Materials

• Gas jars, 2
• Cover glasses, 2
• Nitrogen dioxide (toxic and corrosive)
• Translucent screen and lamp

Health & Safety and Technical Notes

Although nitrogen dioxide is very toxic and corrosive, this activity can be demonstrated without using a fume cupboard. The demonstrator should wear eye protection to handle the concentrated acid.

Read our standard health & safety guidance

You will need a jar of air and a jar of nitrogen dioxide. The latter can be manufactured in the bottom of the jar beforehand (but it must be cooled to room temperature), or it may be poured in.

The illuminated translucent screen behind the jars will make the diffusion easier to see.

Procedure

1. Invert the air-filled jar on top of the jar of nitrogen dioxide.
2. For a litre gas jar, put about 1.5g of copper turnings in the bottom. Add 7 ml of concentrated nitric acid from a 10-ml measuring cylinder. When the gas has almost reached the top of the gas jar, put the inverted gas jar on the top.
3. Observe the consequent diffusion.

Teaching Notes

The advantage of nitrogen dioxide is that it is visible, so students can see diffusion taking place.

This experiment was safety-tested in March 2005