Answer Happy

A species A diffuses radially outwards from a sphere of radius ro. The following assumptions can be made. The mole fraction of species A at the surface of the sphere is Xao. Species A undergoes equimolar counter-diffusion with another species B. The diffusivity of A in B is denoted DAB. The total molar concentration of the system is c. The mole fraction of A at a radial distance of 10ro from the centre of the sphere is effectively zero.
(c) The situation described in (b) corresponds to a roughly tenfold increase in the length of the diffusion path. If one were to consider the case of 1-dimensional diffusion across a film rather than the case of radial diffusion from a sphere, how would a tenfold increase in the length of the diffusion path impact on the molar flux obtained in the 1-dimensional system? Hence comment on the differences between spherical radial diffusion and 1-dimensional diffusion in terms of the relative change in molar flux produced by a tenfold increase in the diffusion path. [4 marks]