Equilibrium Demonstrations

Chemical equilibrium demonstrations show how reactions can reach a balance between forward and reverse processes. They are valuable because equilibrium is an abstract idea that becomes much clearer when seen in action.

Demonstration	Materials	Difficulty	Safety	Summary
Nitrogen Dioxide and Dinitrogen Tetroxide Equilibrium	★★★	★★★	★★★	The equilibrium between brown nitrogen dioxide gas (NO2) and colorless dinitrogen tetroxide gas (N2O4) can be studied in a closed syringe system. Changes in pressure, volume, and temperature shift the equilibrium, which can be observed as changes in the intensity of the brown color.
Blue Bottle Experiment	★★☆	★★☆	★★☆	In the Blue Bottle Experiment, a solution of glucose, potassium hydroxide, and methylene blue alternates between colorless and blue when shaken.
Cobalt Chloride Equilibrium	★★☆	★★☆	★★☆	A solution of cobalt(II) chloride in ethanol appears blue due to formation of [CoCl4]2–. When water is added, the equilibrium shifts toward the hydrated [Co(H2O)6]2+ complex, producing a pink solution.
Equilibrium of Iron (III) Thiocyanate	★★★	★★☆	★★★	The equilibrium between iron(III) ions, thiocyanate ions, and the red-brown ferric thiocyanate complex can be shifted by adding or removing reactants. Color changes from yellow to red-brown or vice versa demonstrate Le Chatelier’s principle in action.

Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories

Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher

Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff