Temperature rate constant dependence

This model permits one to immediately relate the bath frequency spectrum to the rate-constant temperature dependence. For the classical bath (PhoOc < 1) the Franck-Condon factor is proportional to exp( —with the reorganization energy equal to... 

Rate constant temperature dependence Processing threshold Calculation of rate constants at different temperatures, including collision numbers and concentrations of species in steady state Calculation of the rate of photodissociation and cosmic ray-induced molecular processing from photon and particle fluxes... 

Figure 7. Diffusion-disguised rate constant temperature dependence...

At present, the model of solid-state chemical reactions suggested in the literature [48-50] has won certain recognition. McKinnon and Hurd [152] and Siebrand and co-workers [153] compare the mechanism of rate constant temperature dependence by the occupation of the highest vibrational sub-levels of the tunneling particle to that of fluctuation preparation of the barrier the latter Siebrand et al. is preferred. [153] particularly emphasize the experimental proof of the linear dependence of the rate constant logarithm on the temperature predicted by this model. The importance of an account for intermolecular vibrations in the problem of heavy-particle tunneling [48-50] is also noted elsewhere [103]. 

Experiment Relations between decompositian rate and temperature Dependences of reaction rate constants on temperature were evaluated. Experiments... 

Every reaction has its own characteristic rate constant that depends on the intrinsic speed of that particular reaction. For example, the value of k in the rate law for NO2 decomposition is different from the value of k for the reaction of O3 with NO. Rate constants are independent of concentration and time, but as we discuss in Section 15-1. rate constants are sensitive to temperature. 

A thermodynamically unstable structure can exist when its conversion to some other structure proceeds at a negligible rate. In this case we call the structure metastable, inert or kinetically stable. Since the rate constant k depends on the activation energy Ea and the temperature according to the Arrhenius equation,... 

Central to catalysis is the notion of the catalytic site. It is defined as the catalytic center involved in the reaction steps, and, in Figure 8.1, is the molybdenum atom where the reactions take place. Since all catalytic centers are the same for molecular catalysts, the elementary steps are bimolecular or unimolecular steps with the same rate laws which characterize the homogeneous reactions in Chapter 7. However, if the reaction takes place in solution, the individual rate constants may depend on the nonreactive ligands and the solution composition in addition to temperature. 

In addition to temperature, the rate constant also depends on pressure, but this dependence... 

The constant k is used as the rate constant and depends only on temperature and activation energy. If the temperature of a reaction medium is altered, the k value also changes. 

One aspect of determining a rate law is to establish the reaction order. Another is to evaluate the numerical value of the rate constant k. Each reaction has its own characteristic value of the rate constant, which depends on temperature but does not depend on concentrations. To evaluate k for the formation of N02, for instance, we can use the data from any one of the experiments in Table 12.3. Solving the rate law for k and substituting the initial rate and concentrations from the first experiment, we obtain... 

The effect of temperature on the photoinduced electron transfer from [Ru(bpy)3]2+ to methyl viologen solubilized in cellophane has been investigated 98 K The first-order rate constant which depends exponentially on the distance between the reactants shows a non-Arrhenius type of behavior in the temperature interval from 77 to 294 K. This phenomenon, previously found to be of great importance in biological systems, is quantitatively interpreted in terms of a nonadiabatic multiphonon non-radiative process. 

The constant K in this equation, as in some other cases discussed above, denotes the initial reaction rate. Its temperature dependence is described by the standard Arrhenius equation with activation energy U. The constant co characterizing the self-acceleration does not depend on temperature but does depend on the composition of the reactive medium in particular, such factors as the chemical structure and concentration of the curing agent, and the concentration of the catalyst and other components influence the value of co. 

Equation (5.199) shows that the rate constant is dependent on the temperature ... 

If external mass transport limitations strongly dominate, the rate becomes equal to the mass transfer rate, (eq 15). Hence, a first-order dependency is observed and, since the mass transfer coefficient is fairly independent of the temperature the apparent activation energy is negligible. However, due to the existing correlations, the observed rate constant is dependent on the flow rate and particle size. 

G is the ratio of the dimensionless number SD in the disturbed region to its value in the normally-operating part of the bed. SD contains the activation energy, heat of reaction, inlet temperature and bed height, all of which have fixed constant values in all regions of the bed. It also contains the possibly variable quantities C, k and F. C is the average heat capacity of the fluid, and depends on the local phase ratio. kg is the specific rate constant, and depends on the local catalyst density and the phase holdup. F is the local average linear velocity, which can vary from point to point for a variety of reasons. 

The rate constant pcncralls depend-, on ihc absolute temperature, T, Ibllowiiig the I law first propo ed b rrheiiiu-- in 1889 ... 

The rate constant normally depends on the absolute temperature, and the functional form of this relationship was first proposed by Arrhenius in 1889 (see Rule III in Chapter 1) to be ... 

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