Fractional- and Higher-order Reactions

Because of the paucity of data there is no need to discuss reactions of any higher order than third. There are, however, a number of examples in which the order of a reaction has turned out to be fractional, so that it is worthwhile considering the mathematical representation of such relations. If we consider a reaction of arbitrary order n involving a single reactant, the equation may be written 

Except for the case that n is unity, this may be integrated by our usual methods to give 

Some examples of fractional-order reactions are the interconversion of ortho- and para-H [where the rate is %-order n = %)] the gas-phase formation of phosgene, CO + CI2 COCI2 (which has an over-all order of being %-order with respect to CI2 and first-order with respect to CO) and the chlorine-catalyzed decomposition of ozone, 20s 302 (which 

Opposing Reactions. If the products of a chemical reaction may themselves react to reproduce the original reactants, the apparent rate of the reaction will decrease as the reaction products accumulate. Eventually a state of dynamic equilibrium will be achieved in it both of the reactions, forward and backward, will have equal rates. Such systems are subsumed under the category of opposing reactions. Their study is of great interest because the kinetic behavior of these systems can be related to the thermodynamic (equilibrium) properties of the final system. 

Concurrent Reactions. If the reactants may combine with each other in two or more different ways to produce either the same or different products, the over- ill rate of disappearance of reactants will be a composite of the individual reaction paths that are accessible. Such systems are termed systems of concurrent or competing reactions, and their kinetic behavior may 26 

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