Stoichiometric Coefficients and Numbers

We will then see in Example 12.7, and in detail in Chapter 15, how K is used to carry out calculations for this type of equilibrium. 

We define a, b, c, and d in the reaction described by Eq. 12.5.1 as the stoichiometric coefficients. It is, however, more convenient - especially for computer calculations - to write the reaction in the following algebraic form for the general case of k components  

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It is at this point that we depart from the terminology used by Bockris and Reddy (Ref. 3, p. 1007) in their often-cited and generalized discussion of transfer coefficients [Eqs. (la) and (lb)] (i.e., and y ) and introduce the related terms y. and y p. The difference between these sets of electron-number parameters is that in the latter, an electron transferred in a step that occurs, say, v times (i.e., it has a stoichiometric number v greater than 1) is counted only once and not the v times it actually has to occur for one turnover of the overall reaction. This added complication of the electron accounting has the advantage of showing more clearly how stoichiometric coefficients and numbers enter into experimentally obtainable transfer coefficients and hence can demonstrate one of the links between mechanism and experiment. 

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