Introduction
The reaction of hydrogen peroxide with potassium iodide is demonstrated in a tall cylinder. Saturated potassium iodide is added to a mixture of soap, glycerin, water, and hydrogen peroxide. Oxygen and water vapor are trapped in soap bubbles resulting in a long, soapy snake.
2H2O2(aq) —KI Catalyst > 2H2O(g) + O2(g)
A large amount of KI is used and I2 is seen to form, presumably because of the oxidation of I- by the produced O2.
Vomiting pumpkin:
1. Carve the pumpkin and secure saran wrap inside to cover the eyes and nose.
2. Place crystallizing dish inside pumpkin.
3. Use the same amount of soap and KI solutions, but only 75 mL of H2O2solution.
4. If presenting solutions 2 and 3 in cylinders, place cylinders inside beakers to prevent tipping.
5. Place pumpkin on top of an inverted small white tray inside a large white tray with a beige “cafeteria” tray placed flush against the front of the large tray to catch any overflow from the pumpkin’s mouth.
To Conduct Demonstration:
- Pour 125mL of 30% hydrogen peroxide into a tall cylinder containing 100mL of soap solution.
- Carefully add 50mL saturated KI solution to the cylinder. The reaction proceeds very quickly and shoots up and out of the cylinder.
Safety
Goggles should be worn. Wear gloves when handling 30% hydrogen peroxide. Reaction produces heat.
Acknowledgement:
John Farrell, Spring 1991.