Fick's Law of Diffusion - Formula, Application, FAQs

Introduction
In this chapter, we will study about Fick’s Law of Diffusion, Fick’s first law and Fick’s second law. We will study the application of diffusion in material science and learn the concept of molar flux and diffusion.
Before studying the concept of Fick’s diffusion, we should study the concept of Diffusion.

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This Story also Contains

1. What is diffusion?
2. Fick’s Law of Diffusion/ ficks law of diffusion
3. Application of Fick’s Law

What is diffusion?

Diffusion is a process based on the principle of concentration Gradient. In this process there is mass movement of molecules from higher concentration towards lower concentration until it becomes equal. It has a very prominent role in our daily life.
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Molar Flux

Before studying Fick’s Law, we should learn about Molar Flux.

It is the value of the number of moles per unit area per unit time.

Fick’s Law of Diffusion/ ficks law of diffusion

Fick’s law helps us to understand the process of diffusion in detail. It states that: At any time, molar flux is directly proportional to concentration gradient.

Fick’s first law

It states that movement of molecules from higher concentration to lower concentration is governed by:

J=-Dⅆϕ/ⅆx

In the above fick equation, J is diffusion flux

D is diffusivity

Φ is concentration and x is position.

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Fick’s second Law

It state that concentration gradient is related to time, or

,

Where, ∂ϕ/∂t is concentration gradient, D is diffusivity

Both these formulas are called diffusion formula or fick's law of diffusion formula.

RESULT: We can clearly see concentration gradient is proportional to second derivative of concentration gradient with position.

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Application of Fick’s Law

• As we have seen we can calculate change in concentration over any position
• At macroscopic level, it refers to diffusion of two miscible liquid.

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