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Homework Help: Monatomic Idea Gas

  1. Dec 6, 2004 #1
    I am sick of these problems. I just cannot grasp these ideas at all and I'm really trying. But it's no use. And in the end, it's always something minor I'm overlooking.

    I am having issues with the following problem: Three moles of a monatomic ideal gas are heated at a constant volume of 1.90 m^3. The amount of heat added is 5.48 x 10^3 J.

    (a) What is the change in temperature of the gas?

    (b) Find the change in it's internal energy.

    (c) Determine the change in pressure.

    So here's what I know:
    n = 3
    V = 1.90
    Q = 5.48 x 10^3

    So for (a) I believe I need to find (Ti - Tf) The equation I believed I needed to use was W = 3/2nR (Ti-Tf) But that leave me not knowing what W is?

    For (b) I assumed I would use deltaU = 3/2nR DeltaT but this is just a pure guess.

    And for (c) well I have no idea. If I had to guess I would have picked the equation W = P DeltaV but like I said it's just a pure guess.

    I would really appreciate any direction given. It really frustrates me when I can't solve a problem by myself.

    Thanks in advance
  2. jcsd
  3. Dec 6, 2004 #2


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    Homework Helper

    1)Use the first principle of thermodunamics for finite transformations.That formula and the assumtion the volume is left constant (work is 0) should answer point b).
    2)Use the calorical state equation to find the anwer to point a) which requires solving point b) as first,as i indicated.
    3)Use Mendeleev-Clapeyron formula and a bit simple maths to find the expression for the pressure difference.

    Good luck!!
  4. Dec 6, 2004 #3
    Thank you so much. That definitely helped me out.
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