SPECIFIC REACTION RATE CONSTANTS

The batch reactor initially contains 227 kg of acetyiated castor and die initial temperature is 613 K. Complete hydrolysis yields 0.156 kg acetic acid per kg of ester. Eor diis reaction, die specific reaction rate constant k is... 

The termination constants kt found previously (see Table XVII, p. 158) are of the order of 3 X10 1. mole sec. Conversion to the specific reaction rate constant expressed in units of cc. molecule" sec. yields A f=5X10". At the radical concentration calculated above, 10 per cc., the rate of termination should therefore be only 10 radicals cc. sec., which is many orders of magnitude less than the rate of generation of radicals. Hence termination in the aqueous phase is utterly negligible, and it may be assumed with confidence that virtually every primary radical enters a polymer particle (or micelle). Moreover the average lifetime of a chain radical in the aqueous phase (i.e., 10 sec.) is too short for an appreciable expectation of addition of a dissolved monomer molecule by the primary radical prior to its entrance into a polymer particle. 

The initial state-specific reaction rate constant for both diatom-diatom and atom-triatom reactions is calculated by averaging the corresponding cross-section over a Boltzmann distribution of translational energy ... 

The rate constant fe in equation 4.1-3 is sometimes more fully referred to as the specific reaction rate constant, since r = k( when c,- = 1 (i = 1,2,.. . , N). The units of Inland of A) dependon the overall order of reaction, n, rewritten from equation 3.1-3 as... 

Thus, the important conclusion is that the specific reaction rate constant k is dependent on temperature alone and is independent of concentration. Actually, when complex molecules are reacting, not every collision has the proper steric orientation for the specific reaction to take place. To include the steric probability, one writes k as... 

FIGURE 2.2 Arrhenius plot of the specific reaction rate constant as a function of the reciprocal temperature. 

For a temperature of 1000 K, calculate the pre-exponential factor in the specific reaction rate constant for (a) any simple bimolecular reaction and (b) any simple unimolecular decomposition reaction following transition state theory. 

Arrhenius equation jPHYS CHEMj The relationship that the specific reaction rate constant k equals the frequency factor constant s times exp (-AHact/RT), where AHact is the heat of activation, R the gas constant, and T the absolute temperature. ar ra-ne-3s i kwa-zhon ... 

In a purely photochemical reaction the absorption of radiant energy is plainly responsible for the activation. This suggested the possibility that thermal reactions are also due to activation by the thermal radiation which is present at every temperature. The argument was very forcibly presented by Perrin who showed that if the specific rate of a imimolecular gas reaction remains constant, with indefinite diminution in pressure, activation must be by radiation since the number of opportunities for activation by collision also diminishes without limit. In fact, the decomposition of nitrogen pentoxide, the first gas reaction shown to be unquestionably unimolecular, was found to have a specific reaction rate constant over a wide range of pressure, and apparently increasing at very low pressures. ... 

Very many rate processes that proceed at a gas-solid interface obey the Arrhenius equation, which expresses the variation of the specific reaction rate constant k with temperature... 

S, Es values for bimolecular surface rate-controlling step in reaction k specific reaction rate constant... 

The design equations for a CFSTR with perfect mixing, constant fluid density, and steady state operation are as follows. If u is the volumetric flowrate and K = k1/k2, relative reaction rate constant, where k1 k2, and k3 are the specific reaction rate constants for reactions 5-357, 5-358, and 5-359. The rate expressions of A, B, R, S, and T are... 

The specific reaction rate constant k is obtained by multiplying the slope of the straight line by 2.303. 

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