1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Density and r.m.s of an ideal gas

  1. Sep 10, 2014 #1
    1. The problem statement, all variables and given/known data

    A can which is sealed of a volume 0.035m3 contains an ideal gas with a pressure of 150kPa, at a temperature of 350K.
    Calculate the gas density and the root mean squared speed of the gas molecules
    (P.S. the molecular mass is stated as 28)

    2. Relevant equations

    r.m.s=sqrt(3kT/m) density=molar massxP/RxT

    3. The attempt at a solution

    So before this I calculated the number of moles: (150x103)*(0.035)/(8.31*350)= 1.81 moles (3.s.f)
    The number of molecules: N=n*Na=(1.80....)*(6.023x1023)=1.09x1024 molecules (3.s.f)
    The mass of the gas (the molecular mass is stated as 28) mass=n*M=(1.80...)(28)=50.5g (3.s.f)

    For r.m.s, do I simply just have to put the mass I just calculated into the equation? For the density, do I just put the molar mass as 28?

    Thanks for any help in advance!
    Last edited: Sep 10, 2014
  2. jcsd
  3. Sep 10, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    It seems like the following should have been put into the Problem Statement:

  4. Sep 10, 2014 #3
    Sorry I have added it now.
  5. Sep 10, 2014 #4


    User Avatar
    Homework Helper

    In the formula for the rms speed, m is the mass of one molecule.

    As for the density, you calculated the mass of the gas already: it is 50.5 g. The volume of the gas is given. And you certainly know how the density is defined with mass and volume ?

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted