“Chemical waves” experiment
How to make solution change color itself
If you like to watch waves breaking on the seashore, this impressive experiment is for you!
Protective gloves must be worn for this experiment.
Warning! Only under professional supervision.
Reagents and equipment:
- solution of bromomalonic acid (10 g/l);
- solution of potassium bromate (10 g/l);
- ferroin (1% sol.);
Pour the solution of bromomalonic acid (C₃H₃O₄Br) into the cuvette, then the solution of potassium bromate (KBrO₃) and the ferroin (redox indicator), The color of the solution starts to oscillate in waves from red to blue. The effect of colored “waves” is created.
The color of the solution changes from red to blue and back because of the oxidation-reduction reactions taking place in the solution. The iron in the ferroin reacts with potassium bromate and changes from oxidation state +2 (red color – ferroin) to oxidation state +3 (blue color – ferriin).
6[Fe(phen)₃]²⁺ + 6H₃O⁺ + КBrO₃ = 6[Fe(phen)₃]³⁺ + 9H₂O + КBr
Then the complex of iron +3 (blue color) oxidizes the bromomalonic acid, transforming into the complex of iron +2 (red color).
4[Fe(phen)₃]³⁺ + BrCH(COOH)₂ + 7H₂O = 2CO₂↑ + 5H₃O⁺ + Br⁻ + HCOOH + 4[Fe(phen)₃]²⁺
The reagents are distributed in the solution unevenly, so the color changes in waves. Red-blue waves form in the solution, like on the surface of water. The Belousov-Zhabotinsky reaction is one of the most famous chemical reactions in science, and many scientists and groups from different scientific disciplines all over the world have studied it. Thousands and books have been published, and many doctoral dissertations have been defended on the topic. The discovery of the reaction essentially gave impetus to the development of such branches of modern science as synergetics and the theory of dynamic systems and determined chaos.