Arrhenius plot rate coefficient data

Arrhenius plot of rate coefficient data for the reaction + O > Ref. l6, flash photolysis/reso-... 

Figure 29, the Arrhenius plot of these data, yields an adequate exponential fit with a correlation coefficient of 0.973. The fit is neither as good nor as rehable as that of the first-order reaction rate because fewer points were obtainable for either the 200°C reactions - where initiation occurs veiy rapidly, making measurement of the active complex formation difficult - or for the 130°C reactions - where few data points had been collected because of the sluggishness of the reaction at this temperature. 

At high temperatures there is experimental evidence that the Arrhenius plot for some metals is curved, indicating an increased rate of diffusion over that obtained by linear extrapolation of the lower temperature data. This effect is interpreted to indicate enhanced diffusion via divacancies, rather than single vacancy-atom exchange. The diffusion coefficient must now be represented by an Arrhenius equation in the form... 

Fig. 2.6 (a) Desorption kinetic curves at various temperatures under initial hydrogen pressure of 0.1 MPa of the as-received, nonactivated, commercial MgH powder Tego Magnan and (b) the Arrhenius plot of the desorption rate for the estimate of the apparent activation energy, fi, using kinetics data for four temperatures 350, 375, 400, and 420°C (fi -120 kJ/mol). Coefficient of fit = 0.996... 

Fig. 9. Arrhenius plots for the reactions Cl + CH4= HC1 + CH3 (adapted from Heneghanct al, 1981), and OH + CHi HjO + CHj. Solid lines represent TST-based rate coefficient fits to the experimental data (see text). Reprinted with permission from Tully, F. R, and Ravishankara, A. R., J. Phys. Chem. 84, 3126, Copyright 1980 American Chemical Society.

Fig. 10. Arrhenius plots for the reactions HOj + NO OH + NOj (Howard, 1980), C2H3 + O2 CHjO + CHO (Slagle et ai, 1984), and C Clj + 02 =iC0Cl2 + COCl (Russell et al, 1988). Solid lines represent two-parameter (Arrhenius) rate coefficients fits to the experimental data (see text).

Figure 1-17 Rate coefficients (Borders and Birks, 1982) for gas-phase reaction N0 + 03=N02 + 02 in a In versus l/T (K) plot. Two data points with significantly larger errors are excluded. Although the Arrhenius relation (linear relation) is a good approximation, there is a small nonlinearity. The data can be fit well by k = 3.617 exp(-428.7/T) LmoP s Two other relations that can fit the data equally well are In k = 23.18 - 3047.6/(T +138.09), and In k = 30.90 - (1196.4/ T)° 24...

Km . 1.2. An Arrhenius plot of a zeroth-order reaction rate coefficient (normalized to unit surface itiv i atul the unit cell) for the dissolution of a variety of silicate minerals (data from B. J. Wood and I V, Walther, Rates of hydrothermal reaction. Science 222 413 (19K3). See Section 3.1 for additional discussion of rale coefficients for dissolution reactions. 

Following the conceptual idea introduced by Milliken [68], Takahashi and Classman [53] have shown, with appropriate assumptions, that, at a fixed temperature, fc could correlate with the number of C—C bonds in the fuel and that a plot of the log vs number of C—C bonds should give a straight line. This parameter, number of C—C bonds, serves as a measure of both the size of the fuel molecule and the C/H ratio. In pyrolysis, since the activation energies of hydrocarbon fuels vary only slightly, molecular size increases the radical pool size. This increase can be regarded as an increase in the Arrhenius pre-exponential factor for the overall rate coefficient and hence in the pyrolysis and precursor formation rates so that the C/H ratio determines the OH concentration [72]. The ijfc vs C—C bond plot is shown in Fig. 14. When these data are plotted as log vs C—C bonds. 

Considering the results in Table 53, there seems to be very close agreement between measurements of fe2 3 at 300 K from several laboratories. As a result, Smith and Zellner [214] recommend 23= 3.7 x lO at this temperature. The whole series of results in the table is plotted in Arrhenius form in Fig. 72, which shows that the rate coefficient has only a very small temperature dependence, at least up to 500 K. Baulch and Drysdale [178] found that the simplest expression to fit the reliable data adequately over the temperature range 250—2500 K was... 

Fig. 5. Arrhenius plot of the first-order rate coefficients of acetone pyrolysis. Source of the data ...

Fig. 11 Arrhenius-plot relating the parabolic rate constant for the growth ofAl203 scales and data for diffusion in AI2O3, (the scale for the grain boundary diffusion data at the right has been adjusted, so that if 5 = 1 nm, the grain boundary diffusion coefficient corresponds to the bulk diffusion scale) [51].

SCCO2 (full symbols) and of n-lieptane (open symbols) at 50 MPa and various temperatures. The ka data plotted for peroxyesters dissolved in SCCO2 are the experimental values provided by Earner [17]. The rate coefficients for peroxyester decomposition in n-heptane were calculated (for the same temperatures as those selected for the SCCO2 experiments) from the equations reported for kj in n-heptane as a function of pressure and temperature [12, 13]. The dashed lines represent these literature expressions for 50 MPa, whereas the full lines are Arrhenius fits of the measured kj data for decomposition in SCCO2. 

Fig. 1. Arrhenius plot of rate coefficients for the reaction of hydroxyl radical with methane. Symbols are experimentally determined rate coefficients from several different investigations. Solid line is a fit of equation (25) to the data, yielding the equation k (cm molecule Aec ) = 5.7 x 10 T ° exp[—2007(cal)/i 7]. (Reproduced from Smith (1980) with permission of the author.)...

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