20. Observing the Catalysis of Hydrogen Peroxide Decomposition
Goal
To observe the catalytic effect of yeast on the decomposition of hydrogen peroxide.
Method
100 ml 3% hydrogen peroxide solution was poured into a large beaker.
0.25 tsp yeast was added to the beaker. The beaker was gently swirled, and the reaction was observed.
Diagram
Results
3% hydrogen peroxide solution is clear and colorless.
Before the yeast was added to the solution, there was no observable reaction.
When the yeast was added and the beaker swirled, the solution immediately started to bubble very vigorously.
The bubbles gradually died down, but the solution continued to fizz gently for approximately 60 minutes.
The yeast could still be seen in the beaker at the end of the reaction.
Conclusion
Hydrogen peroxide decomposes according to the following reaction:
2H2O2 (aq) → 2H2O (l) + O2 (g)
Therefore oxygen gas was evolved. This caused the bubbling and fizzing.
The decomposition of hydrogen peroxide proceeded much faster after the addition of yeast, but the yeast was not consumed during the reaction, therefore the yeast acted as a catalyst.