4-17. Consecutive Reactions with Two Unknown Concentrations This is a variation on the steady reaction-diffusion system analyzed in Example 4.4-1 and Problem 4-16, in which the concentrations of both participants in the fast bimolecular reaction now are unknown. As shown in Fig. P4-17, it is assumed that species B is generated at a constant rate Ro from a substrate S in a liquid film. Species A enters the film continuously and reacts with B at a rate given by Rva=-kCACB. Aside from the entry of A at x = 0 (where its concentration is maintained at Co), there are no fluxes at the boundaries. A convenient set of dimensionless variables and param- eters is X = L' = 0 kCCB Ro ROL? DACO E = DB kCol? The concentration scale for species B is explained in Example 4.4-1, and once again is the inverse of the Damkhler number for the consumption of B. The bimolecular reaction is assumed to be fast, such that