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Chemical Transformation II
Decomposition of H 2 O 2 with KI
Image courtesy of the Cambridge Science Festival. Used with permission.
Abstract
With the addition of a catalyst, KI, and soap solution, assuming an Ea = 56 KJ/mole and a temperature of 20^0 C, the rate of decomposition of H 2 O 2 to H 2 O and O 2 is increased by 2439 times. This reaction is similar to Chemical Transformation I, where we used MnO 2 to catalyze the decomposition of hydrogen peroxide to create clouds of condensed water vapor.
WARNING NOTICE
The experiments described in these materials are potentially hazardous. Among other things, the experiments should include the following safety measures: a high level of safety training, special facilities and equipment, the use of proper personal protective equipment, and supervision by appropriate individuals. You bear the sole responsibility, liability, and risk for the implementation of such safety procedures and measures. MIT and Dow shall have no responsibility, liability, or risk for the content or implementation of any of the material presented. Legal Notice
Materials
2L Erlenmeyer Flask Dishwashing Liquid Reaction tray Potassium Iodide Gloves Safety Glasses 30% Hydrogen Peroxide 100 mL Graduated Cylinder Food coloring
Safety
30% Hydrogen Peroxide is a strong oxidizer and very corrosive to the eyes, nose, throat and lungs. Contact with any type of combustables may cause fire. Contact with skin will cause burns. Getting it in the eyes can cause irreversible eye damage including blindness. Always wear gloves and safety goggles when working with this material. Potassium Iodide is a potential skin and eye irritant.
Procedure
The reaction should be run on a large reaction tray, which can withstand high temperatures. The tray should be covered with a garbage bag as iodine produced in the foam may stain the floors and table. Carefully pour out 80 mL of 30% hydrogen peroxide into a graduated cylinder. Take the empty 2 L Erlenmeyer flask and carefully pour in the measured 80 mL of hydrogen peroxide. Add about 30 mL of dishwashing liquid. It is not necessary to mix. Add about ten drops of food coloring. In one quick action swiftly add 15 grams of KI and quickly move your hand from the opening of the flask.
Discussion
This is an eye-catching demonstration which produces large quantities of foam which shoot out of the flask 2-3 feet into the air. Immediately after adding the KI the flask will heat up and become hot to the touch. Foam will shoot out of the flask and continue oozing out of the flask for about one minute. This reaction is similar to Chemical Transformation I, where we used MnO 2 to catalyze the decomposition of hydrogen peroxide. In this reaction we changed the catalyst to KI and also added dishwashing liquid to our reaction vessel. The dishwashing liquid complexes with some of the O 2 gas produced in the decomposition resulting in a foaming action rather than the giant cloud of condensed water vapor we saw in Chemical Transformation I. This is another great demonstration to illustrate the effect of the breakdown of H 2 O 2 to H 2 O and O 2 :
MIT OpenCourseWare
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Chemistry Behind the Magic: Chemical Demonstrations for the Classroom
Fall 2012
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