1. The problem statement, all variables and given/known data Molecules with diffusion coefficient of 1.0 x 10^-10 m^2s^-1 are released at a constant rate of 10^10 molecules/s in the middle of a large pool and dffuse away ( assume the 3-dimensional pool is of infinite size). What is the steady state concentration 1 cm away from the source? [Hint: Consider molecules diffusing out through a spherical surface of radius r, with a source at the centre of the sphere]. 2. Relevant equations Fick's First law: Flux = -Dgradient(n) with n being the concentration of the molecules 3. The attempt at a solution I took flux to be equal to the rate at which molecules are being added/surface area of a sphere. Plug it into Fick's first law and then isolate dn/dr (since the source is a point phi and theta should be trivial) and integrate. I have no idea if the assumption that flux = rate/surface area is correct especially since the rate is particles added to the system. If this is not right how should I find the flux? Thank you in advance.