HW2_10 - Second Homework Question I: Thermal Decomposition...

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Second Homework Question I: Thermal Decomposition of HI (7 points) Learning Objective: Different ways to look at the same data: There are several ways to establish the reaction order based on the kinetic data. For example, the reaction order could be calculated from the rate versus concentration data without knowing the rate constant. This analysis does not require integration of the differential rate law. Alternatively, when the rate information is not directly available, the reaction order could be established by testing if a particular kinetic model produces consistent values for the rate constant. The latter calculation typically requires the use of the appropriate integrated rate equation. If the reaction progress is monitored at one initial concentration as a function of time then linear or nonlinear fitting to concentration versus time data yields rate constants. Frequently this is technically impossible. Instead, kinetic data is obtained by carrying out multiple reactions (each with different initial concentration) and the extent of each reaction is determined after stopping each of the reactions. In this scenario, the rate constant is typically determined for each initial concentration based o the integrated rate law solved for the rate constant. The independence of rate constants from concentration or extent of the reaction indicates that a particular kinetic model is appropriate. Analysis of experimental data is complicated because the data always has errors and one must decide if deviations from the data reflect the quality of the experiment or indicate that a model used for analysis is inadequate. A number of statistical tests have been devised to measure the goodness of fit (see http://www.itl.nist.gov/div898/handbook/pmd/section4/pmd44.htm ). Regression analysis often provides a measure of statistical uncertainty for the regression parameters. For example, if we believe that the data is free of systematic errors and the linear regression of log[d C /d t ] versus log[ C ] provides a slope of 1.97 with a standard deviations of 0.05 one would conclude that the reaction is second-order and the small deviation from the expected value 2 is due to random noise in the data. On the hand if the linear regression of data provides a
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This note was uploaded on 01/09/2011 for the course CHEM 111 taught by Professor Kahn during the Fall '08 term at UCSB.

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HW2_10 - Second Homework Question I: Thermal Decomposition...

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