Nitrogen dioxide gas is used to demonstrate Le Chatelier’s principle of equilibrium. The gaseous equilibrium is a mixture of nitrogen dioxide, a brown to reddish brown gas, and dinitrogen tetroxide, a colourless gas.

The preparation and handling of nitrogen dioxide should only be conducted in an operating fume cupboard by trained staff, wearing appropriate PPE.

These laboratory notes provide a method for the generation and collection of nitrogen dioxide (NO₂) gas for two equilibrium demonstrations: the effect of temperature and the effect of pressure.