What is Diffusion?
Before discussing the diffusion of gases, let’s know a bit about what is diffusion? The diffusion is a net movement of atoms or molecules from highly concentrated region to low concentration region. In other words, the movement of atoms or molecules from high chemical potential region to the low chemical potential region.
The word diffusion is derived from a Latin word – diffundere, to spread out. Which means a substance that spreads out or moving from an area to another. Diffusion should not be confused with other transport phenomena like advection or convection, where it use move particles from one place to another in a bulk motion.
The movement of molecules in solids is very small, relatively large in liquids and very large in gases. And this movement of molecules has to lead to a phenomenon called as diffusion.
Diffusion of Gases:
The thermal motion of gas particles at above absolute zero temperature is called molecular diffusion. The rate of this phenomenon movement is a function of the viscosity of the gas, temperature, and size of the particles. The result of diffusion is a slow mixing of materials where the distribution of molecules or atoms are uniform.
Rate of Diffusion:
Rate of Diffusion =
Here is an example to understand the diffusion of gases. Take a container, separating it into two partitions. Keep two gases A and B at same pressure in two parts of the container. The molecules of gas A and B are in continuous random motion in its respective compartments. Now, remove the partition of the container. The molecules of gas A will begin to stray into gas B due to the random motion. In the same way, the molecules of gas B will begin to stray into gas A due to the random motion. As time passes, the molecules of both gases continue to stary each other. In a period of time, the whole mass of gas in the container will be a homogeneous mixture of gas A and gas B and this results because of the phenomenon called as diffusion.