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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

    gneill

    User Avatar

    Staff: Mentor

    Your "EDIT" formula looks promising; Use it in conjunction with the pv = nRt that you mentioned earlier.
     
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