Question

State and explain Fick’s first law of diffusion.

Answer 1

Diffusion occurs in response to a concentration gradient expressed as the change in concentration due to a change in position, . The local rule for movement or flux J is given by Fick's 1st law of diffusion:

in which the flux J [cm-2 s-1] is proportional to the diffusivity [cm2/s] and the negative gradient of concentration, [cm-3 cm-1] or [cm-4]. The negative sign indicates that J is positive when movement is down the gradient, i.e., the negative sign cancels the negative gradient along the direction of positive flux.