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Homework Help: Finding work done & temp change by looking at a plot

  1. Oct 27, 2015 #1
    1. The problem statement, all variables and given/known data
    Refer to plot attached.

    2. Relevant equations
    (a)Find the work done by a monatomic ideal gas as it expands from point A to point C along the path shown in the figure. (The horizontal axis is marked in increments of 25 m3.)
    (b) If the temperature of the gas is 215 K at point A, what is its temperature at point C?
    (c) How much heat has been added to or removed from the gas during this process?
    3. The attempt at a solution
    (a) I know that the area under the curve is the work done so my guess is
    W=P*Vol. Change= 200kpa*25m^3*6.5 squares
    I need to convert this then to MJ
    (b) Completely lost here
    (c) Once i know change in temp I will be able to find Q

    Thank you for all your help in advance!

    Attached Files:

  2. jcsd
  3. Oct 28, 2015 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    What is T in terms of P, V, n? Hint: first you have to find n using the starting temperature of 215K at point A.

  4. Oct 28, 2015 #3
    To do this problem, you need to make the following 2 assumptions:

    1. The pressure in the P-V plot is the external pressure applied to the gas
    2. Point's A and C correspond to thermodynamic equilibrium states of the gas.

    Under assumption 2, you can use Andrew's hint to get the number of moles of gas, and then you can determine the temperature at point C.
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