The Activation Energy of the Pseudo-First Order of a Hydrogen Peroxide-Iodide Reaction

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Abstract: The task of this experiment was to find the activation energy of the pseudo-first order of a hydrogen peroxide-Iodide reaction at 3 different temperatures; 273K, 293K and 303K. Using the arrhenius equation this value was found to be 46.71 J/mole in this experiment. Introduction This experiment focuses on using pseudo-first order kinetics to find the activation energy of a reaction. Psuedo-first order is were one of the reactants in the rate equation is present in great excess over the other in the reaction mixture. Pseudo first order reactions are used to find the rate constant of a second order reaction when one of your two components is very expensive and the other one is relatively inexpensive. You can use an excess of the inexpensive reagent and use a small amount of the expensive one. The arrhenius equation, k' = A*e(-Ea/R*T), was used to determine the activation energy, where; k = rate A = constant Ea = activation energy R = gas constant T = temperature (kelvin) It was re-arranged to, lnk' = lnA - Ea/RT, in order to find Ea Method Please refer to ‘’DCU School of Chemical Science Second Year Chemistry Laboratory Manual Analytical Science 2012-2013’’ pages 64-67 for experimental procedure. Results See Excel sheets. Calculations M of sodium thiosulphate = 0.4977 0.4977/1000 * 0.45 = 2.2365 * 10-4 moles of Iodine = 2. 2365 * 10-4 / 2 = 1.11825 * 10-4 = moles of H2O2 1.11825 * 10-4 * 500 = 0.0559125M lnk = lnA - Ea/RT ln[H2O2]0 = -9.9851 [H2O2]0 = 0.000061 moles/l k = 0.0006 moles/s 5617.7 slope = Ea/R 5617.7 = Ea/8.314 Ea = 46705.56 J/s Ea = 46.705 kJ/mole Theoretical value = the activation energy Ea has been estimated to be 56.5 kJ/mol[2] Discussion: Graphs Upon looking at the obtained graphs, it can be seen that for 30oC the values for ln[H2O2] are much lower than that

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