Under the steady-state condition, Fick’s first law is given as

Where, J = Diffusion flux,

D = Diffusion coefficient,

dc / dx = Concentration gradient

The unit of diffusion coefficient will be:

Concept:

Fick’s Law of diffusion states that “the mass flux of a constituent per unit area is proportional to the concentration gradient”.

where

J = mass flux of constituent per unit area, 

-ve sign indicates that the concentration gradient decreasing in the direction of mass transfer.

Calculation:

∴ 

∴ D = m²/s