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Ideal gas expansion problem

  1. Feb 16, 2013 #1
    1. The problem statement, all variables and given/known data

    Okay so I'm trying to figure out how to get this answer. Theres a souffle made of some ingredients and filled with these ingredients along with some air. Everything starts off at 283.15 K and gets heated in the oven to 463.65 K. Also assume that the air expands with heat as an ideal gas, and the other ingredients' expansion is negligible. Also the volume after heating up is 1.4 times the volume before heating up.

    What we are looking to find is the fraction of the volume of the souffle that is air before being heated up, and the fraction of the volume of the souffle that is air after being heated.

    2. Relevant equations

    PV=T
    PV=nRT

    Vtotal=Vair+Vother
    therefore
    Vtotal-o=Vair-o+Vother
    Vtotal-f=Vair-f+Vother
    also
    Vother-o=Vother-f
    Vtotal-f=1.4Vtotal-o

    3. The attempt at a solution

    So I've messed around with these known equations and legitimately came up with something that I feel is in the right direction of solving the problem. I found that
    1=(Vair-f - Vair-o)/0.4. I figure now that I can use PV=T to get this formula in terms of one variable of the air's volume, however I am not really sure how to do that since I have no value for P. I'm assuming also in this problem that being a souffle, when it heats up the top just tightens to keep the pressure constant.

    So that's all I got. If somebody could help or point me in the right direction for solving this that would be awesome.
     
    Last edited: Feb 16, 2013
  2. jcsd
  3. Feb 16, 2013 #2

    ehild

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    Homework Helper
    Gold Member

    Is the pressure constant during the heating?

    ehild
     
  4. Feb 16, 2013 #3

    Andrew Mason

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    Answer ehild's question and assume that the quantity of air (n) does not change. By what factor does a given volume of air increase in going from 283.15K to 463.65K? Call that x. You can then write out an equation for the volume of the souffle after expansion in terms of the original volumes of air and the original volume of other ingredients.

    AM
     
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