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
Blue Bottle Experiment	★★☆	★★☆	★★☆	In the Blue Bottle Experiment, a solution of glucose, potassium hydroxide, and methylene blue alternates between colorless and blue when shaken.
Carbon Dioxide Equilibrium in Water	★★☆	★★☆	★☆☆	This demonstration uses carbonated water in a sealed syringe with bromcresol green indicator to show how dissolved carbon dioxide affects acidity and how pressure influences solubility. The indicator changes color as CO2 is released, revealing shifts in pH.
Chromate – Dichromate Equilibrium	★★☆	★★☆	★★☆	The equilibrium between chromate (yellow) and dichromate (orange) ions shifts with the addition of acid or base. Acidic conditions favor dichromate, while basic conditions favor chromate.
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.
Copper Complex Equilibrium	★★☆	★★☆	★★☆	A solution of copper ions undergoes visible color changes when ligands such as chloride or ammonia are added. This demonstrates Le Châtelier’s Principle, as the equilibrium shifts to counteract changes in concentration of ligands.
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.
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.

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