Stoichiometric Notation—Multiple Reactions

If more than one reaction is taking place, then a given chemical species, say Au may participate in more than one reaction. This species will, in general, have a different stoichiometric coefficient in each reaction. It may be a product of one reaction and a reactant in another. 

If the index k is used to denote one specific reaction in a system of R reactions, the generalized stoichiometric notation for a reaction becomes 

R is the total number of independent reactions that take place and Vfa- is the stoichiometric coefficient of species i in reaction k. 

Each of the R reactions may contribute to AN,, which is the change in the number of moles of species i. If the extent of reaction k is denoted by lit, then the total change in the number of moles of species i is 

Total change in moles—multiple reactions in a closed system 

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