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Partial Derivative Problem

  1. Mar 2, 2009 #1
    1. The problem statement, all variables and given/known data
    According to the ideal gas law, the pressure, temperature, and volume of a gas are related by PV=kT, where k is a constant. Find the rate of change of pressure (pounds per square inch) with respect to temperature when the temperature is 300[tex]^{o}[/tex]K if the volume is kept fixed at 100 cubic inches.


    2. Relevant equations


    3. The attempt at a solution
    PV=kT
    P=V-1kT
    P=100-1kT
    [tex]\frac{dP}{dT}[/tex]=100-1k

    I don't know how to figure this out. We were given the answer, -.01 psi/[tex]^{o}[/tex]K but I don't know how to get to this with the k there.
     
  2. jcsd
  3. Mar 2, 2009 #2

    Tom Mattson

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    k is Boltzmann's constant.
     
  4. Mar 2, 2009 #3

    Redbelly98

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    This is weird. You're given information (T=300K) which is not necessary for calculating ∂P/∂T, and not given enough information to figure out what k is.

    Moreover, pressure should increase as the gas is heated up. Yet "the answer" is a negative quantity!

    Something is definitely not right here.
     
  5. Mar 2, 2009 #4

    Redbelly98

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    That's what I thought when I first saw the problem. But where is the number of gas molecules in PV=kT? Either that equation was not written correctly, or k really is just "a constant".
     
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