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Chemistry in Quantitative LanguageFundamentals of General Chemistry Calculations$
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Christopher O. Oriakhi

Print publication date: 2009

Print ISBN-13: 9780195367997

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195367997.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 04 December 2021

Chemical Kinetics

Chemical Kinetics

16 (p.229) Chemical Kinetics
Chemistry in Quantitative Language

Christopher O. Oriakhi

Oxford University Press

Chemical kinetics is the aspect of chemistry that deals with the speed or rate of chemical reactions and the mechanisms by which they occur. The rate of a chemical reaction is a measure of how fast the reaction occurs, and it is defined as the change in the amount or concentration of a reactant or product per unit time. The mechanism of a reaction is the series of steps or processes through which it occurs. Most experimental techniques for determining reaction rates involve measuring of the rate of disappearance of a reactant, or the rate of appearance of a product. For a reaction in which the reactant Y is converted to some products: Rate = Concentration of Y at time t2 −Concentration of Y at time t1/t2 −t1 Rate = Δ [Y]/ Δt where [Y] indicates the molar concentration of the reactant of interest, and Δ refers to a change in the given amount. Rate for a reactant, by this definition, is a negative number. For a product, it is positive. The value of the rate at a particular time is known as the instantaneous rate and will be different from the average rate. Its value can be obtained from the plot of concentration (mol/L) vs. time (s) as the slope of a line tangent to the curve at a given point. Consider the following kinetic data for the decomposition of N2O5 to gaseous NO2 and O2 at 40°C (see table 16-3). A plot of [N2O5] vs. time is shown in figure 16-2. From this curve, the instantaneous rate of reaction at any time t can be obtained from the slope of the tangent to the curve. This corresponds to the value of Δ [N2O5]/ Δt for the tangent at a given instant. The instantaneous rate at the beginning of the reaction (t =0) is known as the initial rate.

Keywords:   catalyst, collision theory of reaction rates, energy of activation, order of a reaction, rate constant of a reaction (k)

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