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Unformatted text preview: -1-CHEMICAL KINETICS: H2O2DECOMPOSITION, RATE, AND ACTIVATION ENERGYOBJECTIVE:In this experiment, you will determine the order, rate constant, and activation energy for the reactionbetween hydrogen peroxide and the iodide ion in a basic solution.INTRODUCTION:The reaction to be studied is the decomposition of hydrogen peroxide in the presence of the iodide ion, forwhich the form of the rate equation, the value of the rate constant, and the activation energy will bedetermined.H2O2HH2O + 4O2(g)(1)At the same time, it will be shown that the iodide ion is unchanged in the reaction and is thus a catalyst.Note: There is another similar reaction possible in this system involving H+that also liberates O2. Thesolution will be slightly basic to reduce [H+] and to minimize this possible complication.PROCEDURE:Two reaction mixtures are to be studied. Mixture A and Mixture B. Mixture A will consist of:H2O24 mLH2O 15 mLNaOH (0.2 M)1 mLKI (0.8M) 5 mLMixture A is to be studied at three temperatures:T1= approximately 25°CT2= approximately 35°CT3= approximately 45°CMixture B will consist of:H2O24 mLH2O 10 mLNaOH (0.2 M)1 mLKI (0.8M) 10 mLMixture B will be studied at one temperature: T1= approximately 25°CFor convenience, the four runs can be referred to as A-1, A-2, A-3, and B.Set up the apparatus as shown in Figure 1, making sure that the buret leveling system is free of air bubblesand that the Erlenmeyer flask is centered over the magnetic stirrer and clamped in place so that good,constant stirring can be achieved by the stirring bar in the flask.-2-Transfer the reactants into the Erlenmeyer flask with a pipette in the order: (1) H2O2, (2) H2O, (3) NaOH.Allow a minute or so for them to come to thermal equilibrium with the water bath. Add the KI with apipette, quickly insert the stopper in the tube, close the pinch clamp, and start the stirrer. Start the stopwatch when the water level in the burette reaches 2.00 mL. Record the times of evolution of successive2.00 mL increments up to 20.00 mL. Let the reaction continue to completion and record the final volume ofO2evolved. Throughout the gas evolution and timing, maintain the water level in the leveling funnel at thesame height as that in the burette to ensure that the volume of O2is being measured at a constant pressure.At the start of each test: (1) The Erlenmeyer flask should be clean, dry, and clamped in place in the waterbath over the magnetic stirrer. (2) The stirring bar should be in place at the bottom of the flask with thestirrer off. (3) The water level in the buret should be at 0.00 to 1 mL from the top, and the value should berecorded. (4) The pinch clamp on the two-hole stopper should be open, with the stopper itself hanging just tothe side of the flask (ready to be inserted when the KI is added.)Do test runs A-1 and B (at T1≈25°C). Then heat the water bath slightly to do runs A-2 and A-3. In all casesrecord the temperature of the water bath before and after the kinetic reaction, taking the reaction...
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