Question

How does size of molecule affect diffusion?

Answer 1

`U_(rms)=sqrt((3RT)/(MM))`

Explanation:

The root mean square velocity (`U_(rms)`) of gas particles is given by the following expression:

`U_(rms)=sqrt((3RT)/(MM))`

where,
`U_(rms)` is the rate of diffusion
`R` is the universal gas constant
`T` is the temperature in kelvin
`MM` is the molar mass of the gas

To related this expression to the size of gas particles we can say that bigger size particles will possess high molar mass.

Since, `MM` is inversely proportional to the `U_(rms)`, thus when `MM` increases, the `U_(rms)` will decrease.

Therefore, we can conclude that bigger sized particles (heavy particles) will diffuse slower than lighter particles.