Reaction rate expression

Moore and R. G. Pearson, Kinetics and Mechanism, 3rd Edition, John Wiley Sons, New York, 1981, Chap. 2. 

Integrated expressions applicable to other systems are available.  

Many organic reactions consist of a series of steps involving several intermediates. The overall rate expression then depends on the relative magnitude of the rate constants for the individual steps. The relationship between a kinetic expression and a reaction mechanism can be appreciated by considering the several individual steps that constitute the overall reaction mechanism. The expression for the rate of any single step in a reaction mechanism contains a term for the concentration for each reacting species. Thus, for the reaction sequence  

Capellos and B. N. J. Bielski, Kinetic Systems, Wiley-Interscience, New York, 1972. 

If we specify that the first step is a very rapid but unfavorable equilibrium, and that 2 k, then the second step is rate determining. Under these circumstances, the overall rate of the reaction will depend on the rate of the second step. In the reaction under consideration, the final step follows the rate-determining step and does not affect the rate of the overall reaction does not appear in the overall rate expression. The rate of the reaction is governed by the second step, which is the bottleneck in the process. The rate of this step is equal to 2 multiplied by the molar concentration of intermediate C, which is small and may not be measurable. It is therefore necessary to express the rate in terms of the concentration of reactants. In the case under consideration, this can be done by recognizing that [C] is related to [A] and [B] by an equilibrium constant  

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The algebraic form of the expression (9.24) for the enhancement factor is specific to the particular reaction rate expression we have considered, and corresponding results can easily be obtained for other reactions in binary mixtures, for example the irreversible cracking A—2B. ... 

The two dashed lines in the upper left hand corner of the Evans diagram represent the electrochemical potential vs electrochemical reaction rate (expressed as current density) for the oxidation and the reduction form of the hydrogen reaction. At point A the two are equal, ie, at equiUbrium, and the potential is therefore the equiUbrium potential, for the specific conditions involved. Note that the reaction kinetics are linear on these axes. The change in potential for each decade of log current density is referred to as the Tafel slope (12). Electrochemical reactions often exhibit this behavior and a common Tafel slope for the analysis of corrosion problems is 100 millivolts per decade of log current (1). A more detailed treatment of Tafel slopes can be found elsewhere (4,13,14). 

Reaction Rate Expression 119 Rearranging and integrating Equation 3-28 between the limits gives... 

Reaction Rate Expression 139 Reananging Equation 3-121 and integrating between tlie limits gives... 

Reaction Rate Expression 179 DetcriSunatioin of th pScudo-fiftt... 

Reaction Rate Expression 185 Equating the coefficients of the constant and gives Const 1 = A6b + B (3-268)... 

Reaction Rate Expression Linearizing the rate expression gives... 

Reaction Rate Expression 191 Determine the order of the reaetion and the rate eonstant. Solution... 

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