Hydrogen Peroxide Essay

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13-3 Hydrogen Peroxide Iodine Clock: Oxidation of Potassium Iodide by Hydrogen Peroxide Source: B. Z. Shakhashiri (1992) Chemical Demonstrations: A Handbook for Teachers of Chemistry, vol. 4. pp 37-43. Description: Two colorless solutions are mixed. After 10 seconds, the colorless mixture suddenly turns blue. Concept: Demonstrates a typical clock reaction; shows the effect of the interaction between chemical reactions that have different rates. Materials: • Solution A o 0.6 grams Starch o 30 mLs of Acetic Acid o 4.1 grams of Sodium Acetate o 50 grams of Potassium Iodide o 4.7 grams of Sodium Thiosulfate ▪ Allow mixture to cool and dilute to 1 liter with distilled water o 1 liter flask • Solution B o 500 mLs of 3% Hydrogen Peroxide o 500 mLs of distilled water o 1 liter flask o Safety: Hydrogen Peroxide can be irritating to skin and eyes. Wear safety goggles and gloves. Procedure: Mix the two solutions together. Stir by stir bar and stir plate, swirl the mixture in the flask by hand, or mix by transferring the mixture back and forth between the two flasks. Stir until the colorless solution turns blue (about 10 seconds). Clean-Up: Remaining blue solution can be washed down drain with water . Background: For the entire explanation of this demo see Shakhashiri's Chemical Demonstrations, Vol. 4, pp 42-43. The following is a excerpt from this volume. " The sudden change from colorless to deep blue solutions in this demonstration can be explained with the following sequence of equations[2]: 3 I-(aq) + H202 + 2 H+ (aq) = I3- (aq) + 2 H20 (l) (1) I3- (aq) + 2 S2O3 2- (aq) = 3 I- (aq) + S4O6 2- (aq) (2) 2 I3- (aq) + starch = starch-I5- complex + I- (aq) (3) The first equation indicates that, in an

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