Consider the irreversible conversion of peptide A to B in a stationary liquid film of thickness L, as shown in the figure below. The objective is to determine CA throughout the film and to find the overall rate of product formation. Because the reaction is irreversible, this can be done without calculating CB. The surface at y=0 is assumed to be impermeable and unreactive, and the concentration of A at y=L is specified as C0, which is assumed to be small enough to make diffusion binary. The reaction follows first-order kinetics, with R=kCA. It is assumed that a steady state exists in which CA depends on y only. Figure Sieady diflusion in a liguid film with an imcvenible hempgencous reaction