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Thermodynamics Problem

  1. Feb 6, 2009 #1
    1. The problem statement, all variables and given/known data

    When 1380 J of heat are added to one mole of an ideal monatomic gas, its temperature increases from 272 K to 275 K. Find the work done by the gas during this process.

    2. Relevant equations

    I assume [tex]\Delta[/tex]U = Q - W is the formula to use. But for some reason I'm just confused.

    3. The attempt at a solution

    I tried using 1380 = 275 - W, and got -1105. But that is not the correct answer.
     
  2. jcsd
  3. Feb 6, 2009 #2

    Mapes

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    Can you relate [itex]\Delta U[/itex] to [itex]\Delta T[/itex]?
     
  4. Feb 6, 2009 #3
    That's the problem, I don't understand how they relate. Is there a conversion from Kelvin to Joules? Or do I just use 3K = 1380J - W?
     
  5. Feb 6, 2009 #4

    Mapes

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    Check your book, notes, or reference for an equation of the internal energy (U) of an ideal gas.
     
  6. Feb 6, 2009 #5
    Internal energy increases with increasing temperature, but the exact relation will depend on the type of gas. You should figure out how many degrees of freedom are present in a monatomic gas, then use equipartition of energy to express the internal energy as a function of temperature.
     
  7. Feb 7, 2009 #6

    Andrew Mason

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    You are given Q and you can determine [itex]\Delta U = nC_v\Delta T[/itex]. So it is just a matter of applying the first law to determine W.

    AM
     
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