Hi guys, quick question. I need to find the diffusivity of a species through a sphere (assume the species is concentrated at the center and diffuses outwards in 3D). Im assuming steady-state, so I'm using Fick's First Law, which for 3D scenarios is: J = -D [Del/Nabla Operator]C. First question is, would the equation then be: J = -D[(dC/dx)+(dC/dy)+(dC/dz)]? And if so, how would I go around solving this for J? In this equation, I am accounting for the diffusion in three directions (x,y,z) but the way I see it, they will all be the same (since its a sphere, r is the same for all). Am I correct?

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