Overall and Instantaneous Fractional Yield

The fractional yield of a product is a measure of how selective a particular reactant is in forming a particular product, and hence is sometimes referred to as selectivity.1 Two ways of representing selectivity are (1) the overall fractional yield (from inlet to a particular point such as the outlet) and (2) the instantaneous fractional yield (at a 

For the stoichiometric scheme in Section 5.2.3, the overall fractional yield of D with respect to A, SD/A, is 

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