1. What is Diffusion Flux?

Diffusion flux describes the rate at which particles (atoms, ions, molecules) spread from regions of high concentration to regions of lower concentration. It's governed by Fick's first law of diffusion.

2. How Does the Calculator Work?

The calculator uses Fick's first law of diffusion:

Where:

• \( J \) — Diffusion flux (mol/m²·s)
• \( D \) — Diffusion coefficient (m²/s)
• \( \nabla C \) — Concentration gradient (mol/m⁴)

Explanation: The negative sign indicates that diffusion occurs down the concentration gradient, from high to low concentration regions.

3. Importance of Diffusion Calculation

Details: Calculating diffusion flux is crucial in various fields including chemical engineering, materials science, biology, and environmental science for understanding mass transport phenomena.

4. Using the Calculator

Tips: Enter diffusion coefficient in m²/s and concentration gradient in mol/m⁴. Both values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the diffusion coefficient?
A: The diffusion coefficient (D) is a proportionality constant that relates the diffusion flux to the concentration gradient under steady-state conditions.

Q2: What does negative flux value mean?
A: The negative sign indicates the direction of flux is opposite to the concentration gradient (from high to low concentration).

Q3: When is Fick's first law applicable?
A: Fick's first law applies to steady-state diffusion where the concentration gradient doesn't change with time.

Q4: What are typical values for diffusion coefficients?
A: Diffusion coefficients vary widely: gases (~10⁻⁵ m²/s), liquids (~10⁻⁹ m²/s), solids (~10⁻¹⁴ m²/s) depending on temperature and materials.

Q5: How does temperature affect diffusion?
A: Diffusion rates generally increase with temperature, following an Arrhenius-type relationship where D = D₀exp(-Eₐ/RT).