, Starting with a component mass balance on a spherical shell volume element, derive the transient one-dimensional (in r) mass conduction equation for an isotropic sphere with constant diffusivity of DA (m/s) in which reaction occurs such that component A is generated at a uniform and constant volumetric rate of mgen,a (kg A/m s). Sketch the spherical shell element and label its dimensions, begin with the conservation of mass of A equation written as In - Out + Gen = Acc, explicitly write expressions for the relevant area and volume and derive the final partial differential diffusion equation that could be solved for mass concentration, Ca(r, t) clearly showing each step along the way. Assume Fick's Law applies. (Note Fick's Law written as JA -D gives a mass flux when CA is mass concentration.) dr