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Homework Help: Pressure/Introductory Thermodynamics

  1. Apr 23, 2008 #1
    Not sure what I am doing wrong...

    1. The problem statement, all variables and given/known data
    A chemical reaction takes place in a container
    of cross-sectional area 100 cm2. As a result of
    the reaction, a piston is pushed out through 20
    cm against an external pressure of 567 torr.
    What is the value for w for this reaction?
    (Sign does matter.) Answer in units of J.

    2. Relevant equations

    w = - (Pressure)(Change in Volume)

    3. The attempt at a solution

    Cross sectional area = 100 cm^2 = .01 m^2
    Change is piston distance = 20cm = .2 m

    Pressure = 567 torr x 133.322 = 75593.574 Pa

    Solution disregarding sign = [75593.574 kg/(m*s^2)][.01 m^2][.2 m]

    ---> 151.188 J

    However this is coming up as incorrect.
  2. jcsd
  3. Apr 23, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Looks OK to me. Why are you ignoring the sign when it says "sign does matter"?
  4. Apr 23, 2008 #3
    This is why a separate set of eyes is always helpful!
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