What do you understand by diffusion of a gas and what causes a gas to diffuse

Chris

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What Is Diffusion

Diffusion is the gradual mixing of different substance placed in mutual contact due to the random thermal motion of their constituent particles. Most rapid with gases and liquids, it does also occur with increasing Temperature, the rates at which gases diffuse through a porous membrane vary as the as the inverse of the square root of their MOLECULAR WEIGHT.

Gaseous diffusion is used to separate fissle URANIUM-235 from nonfissle uranium-238, the gas used being uranium hexaflouride(UF6)
 

Chris

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According to Kinetic Molecular Theory, gaseous particles are in a constant state of motion, moving at random speeds and in many different directions. Because of their kinetic energy at temperatures above absolute zero, all particles undergo diffusion.

Diffusion refers to the process of particles moving from an area of high concentration to one of low concentration. The rate of this movement is a function of temperature, viscosity of the medium, and the size (mass) of the particles. Diffusion results in the gradual mixing of materials, and eventually, it forms a homogeneous mixture.

What about Effusion

Not only do gaseous particles move with high kinetic energy, but their small size enables them to move through small openings as well; this process is known as effusion. For effusion to occur, the hole’s diameter must be smaller than the molecules’ mean free path (the average distance that a gas particle travels between successive collisions with other gas particles). The opening of the hole must be smaller than the mean free path because otherwise, the gas could move back and forth through the hole.

Effusion is explained by the continuous random motion of particles; over time, this random motion guarantees that some particles will eventually pass through the hole.
 
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