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Homework Help: Ideal Gas Law

  1. Nov 21, 2005 #1
    I have problem with this ...

    A airmass with the volume 1200m^3 the presswure 101kPa and the temperature 288K moves vertical upwards. The pressure sinks to 80kPa and the temperature sinks to 270K.

    Calculate the new pressure and I know how to use it

    I take 101*1200/288 = 420 Is this right?

    because v1*p1 /t1 = v2*p2/t2
    And how do i make an equation of this?

    and the second question is... how big volume would the airmass had in the normal conditions? Use that to calculate the airs mass...

    And PLEASE no answer like this ... Use the Ideal Gas law... NO **** I had already found out that ...:surprised :surprised :surprised :surprised
  2. jcsd
  3. Nov 21, 2005 #2
    For the first half.. originally, you are given pressure, volume, and temp.
    Pressure and temperature changes, so you should solve for volume, not pressure.

    P*V = n*R*T

    What you DON'T know, and have to calculate with the original three conditions is n*R.

    Same gas, or mixture, n*R will be the same for the new pressure, temp and volume.
    Last edited: Nov 21, 2005
  4. Nov 21, 2005 #3


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    use the combined gas law

    you have everything but v2
    v2 = x (unkown volume)

    (p1*v1)/t1 = (p2*X)/t2 solve for x (rearrange)

    x= (p1*v1*t2)/ (t1*p2)

    make sure your units are right
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