Diffusion of nitrogen dioxide into air
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.
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.
a Invert the air-filled jar on top of the jar of nitrogen dioxide.
b 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.
c Observe the consequent diffusion.
The advantage of nitrogen dioxide is that it is visible, so students can see diffusion taking place.
This experiment was safety-checked in March 2005