Figure 5-7. Transient heat conduction in a solid sheet, with an incident heat flux imposed at one boundary and the other boundary insulated. 5-8. Transient Diffusion in a Film with a Zeroth-Order Reaction Suppose that a liquid film resting on a surface is brought into contact with a gas mixture af t=0. A component of the gas that is absent initially in the liquid is absorbed and undergoes a zerothorder reaction. It is proposed that the reaction-diffusion process be modeled as shown in Fig. P5-7, except with the reaction term given by Da rather than Da. (a) Define the Damkhler number used here. (b) Evaluate the steady-state concentration profile, s(x), and determine Da", the maxinum value of Da for which the proposed problem formulation is valid. (c) Assuming that Da