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EXP2LAPreport - Homogeneous Chemical Equilibrium Mei Huang...

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Homogeneous Chemical Equilibrium Mei Huang TA: Eileen Chen SECTION A5 Chemistry 100A, U.C San Diego April 19, 2008 Abstract: It is important to know the calculation of Kc value from a chemical reaction. In this experiment, The theory of the Kc is independent of the initial concentrations of reactants and products is also needed to be proved in this experiment by titrating five different flasks which containing five different concentration of reactants and products with NaOH. The Kc was determined to be 6.293, and the theory was disproved with the result from the experiment. Introduction: In chemical reactions, there are reactant and products. It is easy to assume that the reactants are converted entirely to products following the stoichiometry of the balanced chemical equation. However, the direction of the reaction is not always going from reactants to products completely. The direction of the reaction is affected by the conditions, such as temperature and pressure, and the initial concentrations of the reactants and products. An equilibrium constant Kc which is a numerical ratio to show the relative concentration of all species is determined. In a chemical reaction like this: aA + bB <-- cC+ dD, Its Kc = (C) ^c (D)^d/(A)^a(B)^b A large Kc means there are high product and low reactant equilibrium concentration. A small Kc value means there are small equilibrium concentrations of products and large amount of concentration of reactants. A moderate Kc values which is between 0.001 and 100 is studied in this experiment. The purpose of this experiment is to determine the equilibrium constant for the esterification reaction of ethyl alcohol and acetic acid to produce ethyl acetate and water. HCl is used as a catalyst in this reaction: C2H5OH+CH3CO2H<==> CH3CO2C2H5 + H2O The theory of the Kc is independent of the initial concentrations of reactants and products is also needed to be proved in this experiment by titrating five different flasks which containing five different concentration of reactants and products with NaOH. Before doing this, a standardization of NaOH needed to be done in order to determine the concentration of the NaOH. KHP is used to determine the concentration of the NaOH. Because in the reaction between NaOH and KHP, the mole ratio between NaOH and KHP is 1:1, the moles of KHP is used is equal to number of moles of NaOH. Therefore, the NaOH’s concentration can be determined. An indicator phenolphthalein is used. The reaction’s equilibrium point is occurred when the indicator turns faded pink. There are total 3 trials are done for the NaOH standardization because the more trials are done, the
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more accuracy it is. Then, the titration between NaOH and the five flasks are done in order to determine the number of moles of each reagent, so that the Kc value can be determined. Experimental:
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This note was uploaded on 06/04/2008 for the course CHEM 100A taught by Professor Dai during the Spring '06 term at UCSD.

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EXP2LAPreport - Homogeneous Chemical Equilibrium Mei Huang...

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