\[J=-D\frac{\Delta C}{\Delta x}\]
Variables
Jdiffusion flux (mol/m²·s)
Ddiffusion coefficient (m²/s)
dCconcentration difference (mol/m³)
dxdistance across which diffusion occurs (m)
Description
What is this formula?
Fick's diffusion flux formula calculates the amount of substance crossing a unit area per unit time due to a concentration gradient.
When to use it
Use this formula in biophysics, physiology, membrane transport, or chemical diffusion problems when a concentration gradient drives molecular movement.
Example
A molecule diffuses with:
D=2.0×10^-9 m²/s
dC=-50 mol/m³
dx=0.01 m
Formula:
J=-(D*dC)/dx
Substitution:
J=-(2.0×10^-9*(-50))/0.01
Result:
J=1.0×10^-5 mol/m²·s
The diffusion flux is 1.0×10^-5 mol/m²·s.
Applications
- Cellular transport analysis
- Membrane diffusion
- Respiratory gas exchange
- Drug delivery modeling
- Biophysical mass transport