Relative Effusion Rate

[Spiker]

Why does partial pressure not affect relative effusion rate? Say molecular weight of gas A is 4 times as much as gas B. So gas B is twice as fast. However if there are twice as many A (partial pressure twice of the B) Then why wont A effuse more molecules more time period? Take it to extreme if there is only 1 molecule of B wont it take a long time for B to find the hole?

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[dragon529]

I can only argue with the equation v=sqrt(3RT/M) and there's no moles or concentration in that equation.. can anyone come up with a better explanation?

 

[pmahesh107]

Effusion rate is talking about how much of a specific substance will go through the hole per unit time. For example, the unit could be mols/min. This means it is independent of the quantity of the substance you have since it is included in the units

 

[minutemen11]

i dont get this this either.. actually i think i dont get what the orginal question is. The way i think of it is.. the KE for all the gas molecules at a given T is the same. So those that are more massive will move slower; rate1/rate2= sqrt M2/M1 how does this relate to partial pressure aka. concentration? That is what i dont understand.

On the other hand, if you only had 1 molecule of B then there would be 2 molecules of A, since A is heavier it will not travel as far around the container and the molecules will have a less likely chance of a hitting a pore? Someone clarify?

 

[G1SG2]

I think mass outweighs partial pressure. Yeah, the partial pressure of A may be greater than that of B BUT A is still heavier than B, which slows it down.

"Take it to extreme if there is only 1 molecule of B wont it take a long time for B to find the hole?"

Not necessarily, since B is faster!! It will outrun the two fat A molecules.