Rate of reaction specific

Chemical kinetics is a part of chemistry that studies the change in time of the composition of a reacting system. The specific rate of reaction (see Appendix H for details) is expressed as ... 

Ross, A. B. (1975), Selected Specific Rates of Reactions of Transients from Water in Aqueous Solution. Hydrated Electron, Supplemental data, NSRDS-NBS 43, Supplement, National Bureau of Standards, Washington, D.C. 

Watson, C., Jr., and Roy S. (1972), Selected Specific Rates of Reactions of the Solvated Electrons in Alcohols, NSRDS-NBS 42, U.S. Government Printing Office, Washington, D.C. 

A reagent in solution can enhance a mass transfer coefficient in comparison with that of purely physical absorption. The data of Tables 8.1 and 8.2 have been cited. One of the simpler cases that can be analyzed mathematically is that of a pseudo-first order reaction that goes to completion in a liquid film, problem P8.02.01. It appears that the enhancement depends on the specific rate of reaction, the diffusivity, the concentration of the reagent and physical mass transfer coefficient (MTC). These quantities occur in a group called the Hatta number,... 

Conditions existing at the triple interface, Ag/AgX/Solution, will influence the rate at which the catalyzed reaction occurs. These conditions will determine the activity of the silver ions, the concentration of adsorbed developer, and the state of the catalyst. The halide ion will be an important factor in determining the activity of the silver ions, and Sheppard has suggested that the hydration and diffusion away of the halide ion is the dominant factor in determining the specific rate of reaction at the interface (Sheppard, 15). The known order of reactivity of the halides, AgCl > AgBr > Agl, follows as a natural consequence from this point of view, whereas it would not be predicted on the basis of the electrode mechanisms. 

At any radius r, the rate of reaction per unit area can be calculated from the quotient, (dn/dt)r/Sr. Consequently, the specific rate of reaction and calculated carbon dioxide concentration (both taken at the same value of r) can be plotted to determine the true order of reaction, independent of diffusion control. Figure 19 presents such data for the carbon rod reacted at 1200°, assuming the relative concentrations for Case 3 in Table VI to be applicable. From an auxiliary plot similar to Fig. 19, a finite reaction rate at zero carbon dioxide concentration is found. Since the concentrations of carbon dioxide were calculated assuming Co to be zero, it is clear that this reaction rate is due to a finite Co concentration at the center of the rod. The actual values of concentration at values of r were estimated by extrapolat-... 

Specific rates of reactions of practical interest cannot be found by theoretical methods of calculation nor from correlations in terms of the properties of the reactants. They must be found empirically in every case together with the complete dependence of the rate of... 

As discussed before, the rate of an enzyme-catalysed reaction is dependent, not only on the substrate concentration at any instant, but also on the temperature, pH and the degree of decay of that enzyme. For given values of pH and temperature, the specific rate of reaction v is given, in the simplest case, by the Michaelis-Menten equation ... 

Farhataziz and A.B. Ross. 1977. Selected specific rates of reactions of transients from water in aqueous solution. III. Hydroxyl and perhydroxyl radical. National Bureau of Standards NSRDS-NBS59. Washington, DC. 

Process intensification can be considered to be the use of measures to increase the volume-specific rates of reaction, heat transfer, and mass transfer and thus to enable the chemical system or catalyst to realize its full potential (2). Catalysis itself is an example of process intensification in its broadest sense. The use of special reaction media, such as ionic liquids or supercritical fluids, high-density energy sources, such as microwaves or ultrasonics, the exploitation of centrifugal fields, the use of microstructured reactors with very high specific surface areas, and the periodic reactor operation all fall under this definition of process intensification, and the list given is by no means exhaustive. 

Ross AB. Selected specific rates of reaction of transients from water in aqueous solution. Hydrated electron, supplemental data. Natl Stand Ref Data Ser, Nat Bur Stand (US) 1973 43(Suppl) 43 pp. 

In solving this set of equations we can neglect fluorescence and deactivation of excited Bra molecules so that the specific rate of reaction 1 == 2/a, where is the average number of moles of photons absorbed per cc per second. It is also convenient to assume that a constant fraction of the Br atoms striking the wall is captured to ultimately form Bra, whereas this accommodation coefRcicnt must certainly depend on the stationary-state concentration of 13r atoms, the chemical nature of the wall, the concc iitrations of other species which may affect the adsorption of Br atoms, etc. 

Now consider the maximum temperature difference at the stationary state for liquids [Eq. (XIV.2.7)] and assume for convenience that we have a reaction of half-life = 1 hr (fc = 0.69// = 2 X 10 sec ) and a reactive concentration of 0.05 mole/liter such that the average specific rate of reaction R will be about 1 X 10 mole/cc-sec. If we further assume a heat of reaction // = 10 Kcal/mole and take K = 1.0 X 10 , we find for ro = 5 cm... 

Still, some conclusions can be drawn. In the mixtures, specific rate of reaction is more a function of carbon number than of degree of branching, and the effect of carbon number in mixtures is not greatly at variance with the conclusions of Ref. 3. Specific rates of individual compounds in the mixtures appear to be somewhat lower than we would predict from Equation 13. This can perhaps be partially attributed to the effects of nitrogen diluent. 

Thus far, the discussion of reaction rate has been confined to homogeneous reactions taking place in a closed system of uniform composition, temperature, and pressure. However, many reactions are heterogeneous they occur at the interface between phases, for example, the interface between two fluid phases (gas-liquid, liquid-liquid), the interface between a fluid and solid phase, and the interface between two solid phases. In order to obtain a convenient, specific rate of reaction it is necessary to normalize the reaction rate by the interfacial surface area available for the reaction. The interfacial area must be of uniform composition, temperature, and pressure. Frequently, the interfacial area is not known and alternative definitions of the specific rate are useful. Some examples of these types of rates are ... 

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