DESCRIPTION: This experiment compares inorganic catalysts and enzymes in terms of their effect on the decomposition of hydrogen peroxide.
Materials Needed ( for a class of 30)
1000 ml of 6 % hydrogen peroxide Test tube rack
5 g of solid MnO2 5 g of solid FeCl3
5 ml blood from uncooked meat Paring knife
One each of banana, potato, pineapple and apple
7 large test tubes x 5 lab groups = 35 total
HAZARDS: Use caution with hydrogen peroxide. It can cause eye and skin irritations and is an oxidizer. Avoid contact with ferric chloride as it is a tissue irritant.
PROCEDURE
Part A
Place 5 ml of the hydrogen peroxide in each of the 7 test tubes. Add the catalysts according to the chart below:
| Substance | Inorganic catalyst or enzyme? | Amount of gas produced? |
| a pinch MnO2 | 1. | 1. |
| a few crystals FeCl3 | 2. | 2. |
| chunk of potato | 3. | 3. |
| chunk of apple | 4. | 4. |
| chunk of banana | 5. | 5. |
| 3-4 drops of blood | 6. | 6. |
| control (nothing added) | 7. | 7. |
Observe the rate of oxygen gas produced in each tube. Make comparisons between the organic enzymes as opposed to the inorganic catalysts in rate of production of gas.
Part B
Repeat the procedure for part A, except boil the catalysts before adding to the hydrogen peroxide. DO NOT HEAT THE HYDROGEN PEROXIDE.
Put the catalyst substances in each of the six test tubes and boil for five minutes in a 250 ml beaker half filled with hot water bath. Add the hydrogen peroxide after the substances have cooled. Record the reactions of the hot catalysts with new samples of each of the materials used in Part A.
Reactions with Hot Catalysts
| Substance | Inorganic catalyst or enzyme? | Amount of gas produced? |
| a pinch MnO2 | 1. | 1. |
| a few crystals FeCl3 | 2. | 2. |
| chunk of potato | 3. | 3. |
| chunk of apple | 4. | 4. |
| chunk of banana | 5. | 5. |
| 3-4 drops of blood | 6. | 6. |
| control (nothing added) | 7. | 7. |
DISPOSAL: Any solids can be disposed in the wastebasket. Liquids may be washed down the sink.
DISCUSSION
It is interesting to note the wide variety of substances which catalyze the breakdown of hydrogen peroxide into water and oxygen gas, H2O2 ---> 1/2 O2(g) + H2O
Not only by various metal salts but also the catalase enzyme which is widespread throughout the living kingdom. There is some logic to this in that hydrogen peroxides strong oxidizing nature tends to make it a toxic substance. Interestingly the action of hydrogen peroxide on open cuts is due to the catalase in our blood, not due to bacteria. The hydrogen peroxide acts as a disinfectant because bacteria lack the enzyme to render it harmless. thus the bacteria are killed, while our catalase protects us. Not every bacteria is killed in this fashion. Bacteria can be categorized as "catalase positive" or "catalase negative" using a procedure much like this lab. The body can also produce its own hydrogen peroxide which can be used to attach foreign cells at the molecular level. The hydrogen peroxide is particularly effective in reacting with the biomolecules with carbon carbon double bonds.
REFERENCE: Bob Dayton, Henrietta H.S. , Webster, NY 14580 and John Whitsett, Central HS, Onalaska, WI 54650