Homework Help: Phase cells and equilibrium speed distribution

1. Jan 15, 2010

michelle001

1. The problem statement, all variables and given/known data
If the probability of any given molecule occupying any given phase cell is known, what additional information is required in order to work out the equilibrium distribution of molecular speeds in a pure gas?

2. Relevant equations

3. The attempt at a solution
Since the phase cells describe the position and velocity of each molecule - the speed of every molecule can be determined so long as the atomic mass is know. Since we know all phase cells we know number of molecules and the probability of each and can find the spread of speeds. So the only additional information required from that supplied in the question is the atomic mass of the molecule

I can't actually find any information to support this but having tried to figure it out and reread books for last two hours I thought I'd try my first post!! can anyone help me??

or having had another think am I supposed to use f(v)=Bv^2 . e^(-mv^2/2kT) in which case I'd need the absolute temperature and atomic mass of neon?

thanks

Last edited: Jan 15, 2010
2. Jan 18, 2010

tomwilliam

Hi Michelle
I'm not an expert, but I think we're doing the same course.

If you look at the equation that you stated for the speed distribution function f(v), you need to work out what the different parts of it relate to. e^-mv^2/2kT corresponds to the probability of a molecule being found in a given phase cell, so have a think about what other items of information are needed to find f(v).
Hope that helps