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: Volume of a mole of air 15km above sea level

  1. May 11, 2012 #1
    1. The problem statement, all variables and given/known data

    one mole of an ideal gas takes up 0.0225m3 at 0 degrees celsius and 1.01x10(5) pascals. (calculated)
    hence, calculate the volume of 1 mole of air (ideal) at an altitude of 15km above sea level.
    average molecular mass of air = 29 amu.
    T @ altitude of 15km = 0 degrees C.

    2. Relevant equations

    I used pv=nrt for the first part.
    another equation i can find is

    M = m N A
    where M is the mass of the mole in kg, m is the atomic mass unit in kg, N is the atomic mass, and A is avogadros constant.

    3. The attempt at a solution

    volume of a mole of air can be calculated using pv=nrt, rearranged for v which is v=nrt/p.
    however, i have no idea how to bring the altitude into it!

    thanks for help!

    Edit: Perhaps equation P = P0 exp (-mgy/k(b) t)?
    where m = average molecular mass in kg, g = acceleration due to gravity, y = altitude in m, kb is boltzmanns constant and t is temperature?
    but i'm not sure where to find volume.
    Last edited: May 11, 2012
  2. jcsd
  3. May 11, 2012 #2


    User Avatar

    Staff: Mentor

    Your "EDIT" formula looks promising; Use it in conjunction with the pv = nRt that you mentioned earlier.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook