Equimolar counterdiffusion of A and B occurs through a spherical film of i.d=ri and thickness δ. The flux of A is NA1 at r=ri. The flux through a flat film of the same thickness is NA2. if NA1 is larger than NA2 by 5%, the film thickness δ is
(a) 0.025ri
(b) 0.05ri
(c) 0.1ri
(d) 0.01ri
This question was posed to me in a national level competition.
This key question is from Diffusion through Variable Area in chapter Diffusion in Solids and Molecular Diffusion in Fluids of Mass Transfer