[confusedstud]

Why doesn't the density affect the rate of diffusion? Since a denser air should sink, so if I have a upright container with two different gases shouldn't the denser air sink down while the less dense one rise up? So no homogenous mixture should form? Thanks! 

[Borek]

In very low temperatures and in very high columns there is some separation observed (such process is called cryogenic distillation), but in normal conditions thermal motions of the molecules mix gas way too efficiently.

[confusedstud]

In very low temperatures and in very high columns there is some separation observed (such process is called cryogenic distillation), but in normal conditions thermal motions of the molecules mix gas way too efficiently.

Hi but when collecting gases, we sometimes use the density property to collect them (either rise up into the container or sink down) so why in this case it is able to be contained in this manner? Thanks Borek :smile:

[Arkcon]

Certainly, when we constantly generate a gas, it can displace air from a small container, or when a tank valve fails, gas can fill a local area, which can be dangerous, with risks depending on the gas.  But over a reasonable period of time, diffusion does balance out gasses over a wide area, for example, dense gasses from the atmosphere don't accumulate at our feet on the surface of the Earth.