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
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 Fall '08
 KAHN
 Reaction, Kinetics, Rate equation, George Kistiakowsky

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