Eduard-Job-Foundation for Thermo- and Matterdynamics

Experiment 19.1: Decomposition of Hydrogen Peroxide by Various Catalysts

Catalysis.jpg

Procedure:
Hydrogen peroxide solution is filled into each of the three goblets. Iron(III) chloride solution is added to the first solution and a spatula-tip full of manganese dioxide to the second. Finally, catalase solution is dropped into the third goblet.

Observation:
A temporary color deepening occurs in the first goblet. Additionally, a noticeable evolution of gas starts after a short while. A strong effervescence combined with the formation of fog can be observed in case of the second goblet. The liquid gets dark because of the manganese dioxide. In case of the third goblet, a strong evolution of gas combined with the formation of mist is observable.

Explanation:
Hydrogen peroxide exhibits a strong tendency to decompose into water and oxygen (disproportionation):

formel_h202.jpg

As there is a potential drop, the reaction principally can occur spontaneously. The decomposition rate at room temperature is, however, very small. But the rate can be appreciably increased by the addition of a catalyst.

Fe3+ ions are an example for a homogeneous catalyst, manganese dioxide, however, for a heterogeneous catalyst. Enzymatic catalysis takes an intermediate position.

Video (mpg4, 3:19)