Homework Help: Ideal Gas

1. Feb 27, 2013

AllenHe

1. The problem statement, all variables and given/known data
The ideal gas has a density of 2.4 kgm–3 at a pressure of 2.0 × 105 Pa and a
temperature of 300 K.Find the root mean square speed of the gas atoms.

2. Relevant equations

p=(1/3)*(Nm/V)*v(squared)

3. The attempt at a solution
I tried to make v(squared) the subject, but N(the number of atoms) is not given, and when I looked at the answer, it made v(squared) the subject, and omitted N. I don's understand why do they have to omit N, is it because we are suppose to find the speed for one atom?

2. Feb 27, 2013

cepheid

Staff Emeritus
Well, N/V is the number of particles per unit of volume. If you multiply this by m, the mass per particle, you get the mass per unit volume. What's another name for that?

3. Mar 9, 2013

AllenHe

Thanks

Oh, I get it, so you mean the density is mN/v, right?

4. Mar 10, 2013

sankalpmittal

Yes, he means that in,

P= mnvrms2/3V

Density is mn/V

m=molar mass
n=number of moles

But you have written N=avogadro's number
m=mass of one molecule ?

Are you giving this formula for 1 mole of gas ?

5. Mar 10, 2013

cepheid

Staff Emeritus
Yes, that is exactly what I meant :)

6. Mar 10, 2013

cepheid

Staff Emeritus
The OP explicitly stated that N was the total number of atoms. So this problem isn't doing anything with moles.