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where R is the gas constant per mole ; T is the absolute temperature ; 

 N is Avogadro's number; and h is Planck's constant. The term AS t 

 represents the contribution to the entropy of A ■ B % due to motion along 

 the reaction coordinate. (Note: &S t is a part of the partial molai 

 entropy of the activated complex A-B*.) The reasoning necessary to 

 obtain the absolute rate of breakdown of the activated complex has been 

 presented in several equivalent forms by Eyring and his co-workers. 

 All these developments involve more quantum mechanics than can be 

 included in this text. 



If the reaction is not diffusion controlled, A ■ B* may be thought of as 

 being in quasi-equilibrium with the reactants A and B. As demon- 

 strated in the last chapter, this allows one to write 



__ [A-B \ -ag°IRT (1\ 



[A][B] ' [ } 



where AG is the difference in the standard state between the free 

 energy of AB* and A + B. Because the factor —ASJR appears 

 shortly, it is convenient to divide AG as 



AG = AG* + T\S t 



where the activation free energy AG* is computed, omitting the con- 

 tribution to the entropy from the reaction coordinate. Equation 7 may 

 be rewritten 



[A-B*] = [A][B]e- GtlRT e- AS < IR 



The absolute rate of transformation of A-B* to C leads one to the 

 expression 



From this equation, one finds that 



* ~ [A][B] dt ' Nh K ' 



The term AG* may be replaced as before giving 



k = ^L e -AH*IRT e AS^R ( 9 ) 



Nh 



