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Title:A Direct Determination of the Activation Energy for the Reaction of Nitric Oxide With Ozone
Author(s):Borders, Richard Arnold
Department / Program:Chemistry
Discipline:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Chemistry, Analytical
Abstract:The activation energy for the reaction of nitric oxide with ozone has been directly measured as a function of temperature. This requires the construction of an instrument which can simultaneously measure the ratio of the reaction rates at two temperatures. The instrument constructed for this study consisted of two flow tubes that are connected together at each end, where the reaction zone temperature of each flow tube was controlled independently. The reaction of nitric oxide and ozone was pseudo-first order ({NO}/{O(,3)} (GREATERTHEQ) 250) and studied by following the reduction of the chemiluminescence of one of the products (NO*(,2){('2)B(,1,2)}) of the reaction.
The chemiluminescence was measured using a microcomputer-controlled photon counter designed for these studies. This photon counter is capable of detecting a single pulse with an amplitude of (GREATERTHEQ) 100 (mu)V, typically has a pulse pair resolution of 10 ns for 350-(mu)V to (GREATERTHEQ)40-mv pulses, and can operate to > 250 MHz with periodic input pulses of (GREATERTHEQ) 40-mV.
which has a variance of 0.061 x 10('-28)cm('6) molecule('-2)s('-2).
The activation energy has been found to vary with temperature. The activation energy varies from 2390 (+OR-)10 calories at 216 K to 2970 (+OR-)60 calories at 333 K. The variation over the complete temperature range studied (204-353 K) is large enough (650 calories) that the errors associated with the method cannot account for all of the variation. There are other pathways for this reaction other than ground state reactants going to ground state products, and their contribution to the activation energy ((TURN)500 calories) has been found to be sufficient to account for the observed variation with temperature when added to the variation predicted by either transition state (180 calories) or collision (150 calories) theory.
The best fit for the rate constants measured in this study is
(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI)
which has a variance of 0.0077 x 10('-28) cm('6) molecule('-2)s('-2). This fit overestimates the temperature dependence of the activation energy. The best fit to the rate constants for predicting the activation energy is
(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI)
which has a variance of 0.010 x 10('-28) cm('6) molecule('-2)s('-2).
A conventional Arrhenius fit to the data is
(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI)
Issue Date:1981
Type:Text
Language:English
Description:187 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
URI:http://hdl.handle.net/2142/67287
Other Identifier(s):(UMI)AAI8203409
Date Available in IDEALS:2014-12-13
Date Deposited:1981


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