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Don't Be Tricked by Your Integrated Rate Plot!
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Abstract
Reaction order can be determined from kinetic data in a variety of ways. Two common methods are comparison of initial rates (while varying reactant concentration) and plotting integrated rate expressions. Both of these are introduced in general and physical chemistry textbooks. However, the limitations of the integrated rate plot approach are generally not covered. For the integrated rate plot to be used to confirm first-order kinetics, at least 4-5 half-lives' worth of data are required. Deviations from linearity between first- and second-order analyses of first-order data are not observed until the third half-life. Moreover, such deviation may be masked by indeterminate error. These points are demonstrated using simulated first-order kinetic data when conditions are idealized and when a random error of up to ±10% is introduced into the concentration values.
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Keywords (Audience):
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Textbooks / Reference BooksKeywords (Subject):
KineticsCiting Articles
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This article has been cited by 9 ACS Journal articles (5 most recent appear below).
Reaction Order Ambiguity in Integrated Rate Plots
Joe LeeJournal of Chemical Education2008 85 (1), 141Reaction Order Ambiguity in Integrated Rate Plots
Joe LeeJournal of Chemical Education2008 85 (1), 141Integrated rate plots are frequently used in reaction kinetics to determine orders of reactions. It is often emphasised, when using this methodology in practice, that it is necessary to monitor the reaction to a substantial fraction of completion for ...
A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter
Lars Wadsö , Xi LiJournal of Chemical Education2008 85 (1), 112A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter
Lars Wadsö , Xi LiJournal of Chemical Education2008 85 (1), 112Most processes (whether physical, chemical, or biological) produce or consume heat: measuring thermal power (the heat production rate) is therefore a typical method of studying processes. Here we describe the design of a simple isothermal heat conduction ...
New Highlights on Analyzing First-Order Kinetic Data of the Peroxodisulfate-Iodide System at Different Temperatures
J. Yperman , W. J. GuedensJournal of Chemical Education2006 83 (4), 641New Highlights on Analyzing First-Order Kinetic Data of the Peroxodisulfate-Iodide System at Different Temperatures
J. Yperman , W. J. GuedensJournal of Chemical Education2006 83 (4), 641A pseudo-first order kinetic experiment examining the peroxodisulfate–iodide system was performed using an automated undergraduate chemistry lab experiment. The kinetic study was executed at different temperatures. This format makes it possible to ...
First-Order or Second-Order Kinetics? A Monte Carlo Answer
Joel TellinghuisenJournal of Chemical Education2005 82 (11), 1709First-Order or Second-Order Kinetics? A Monte Carlo Answer
Joel TellinghuisenJournal of Chemical Education2005 82 (11), 1709In chemical kinetics, data for the concentration [A] as a function of time can be analyzed by least-squares fitting to the appropriate expression for the integrated rate law. The problem of discriminating between first and second order in such analyses is ...
Don't Be Tricked by Your Integrated Rate Plot (the author replies)
Edward UrbanskyJournal of Chemical Education2004 81 (1), 32Don't Be Tricked by Your Integrated Rate Plot (the author replies)
Edward UrbanskyJournal of Chemical Education2004 81 (1), 32Reply to comments on an earlier published article.
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- Received: August 03, 2009
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