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Homework Help: PV=nRT problem

  1. Dec 9, 2014 #1
    1. The problem statement, all variables and given/known data
    If 1.15 moles of an ideal gas has a pressure of 3.60 atm, and a volume of 81.37 L, what is the temperature of the sample in degrees Celsius?

    2. Relevant equations
    p = pressure
    v = volume
    n = number of moles
    r = 0.08206 L atm/(mol K)
    T = ?

    3. The attempt at a solution
    So I did the problem by :
    3.60 (81.37) = (1.15)(0.08206)(T)
    I found T to be 20.9 degrees K. I converted the temperature from K to C by doing K = C + 273 so 20.9 = C + 273. So the temperate in C is -252 degrees. However, I am still getting this wrong in the online homework. Can anyone help me figure out mistake?
  2. jcsd
  3. Dec 9, 2014 #2
    You did the arithmetic incorrectly. That's all.

  4. Dec 9, 2014 #3
    I have done the problem multiple times and am unsure of where my arithmetic problem is.
  5. Dec 9, 2014 #4
    Well, your equation should give the correct temperature, which is in the 200's. I guess the only what we can help you further is if you show the individual steps in your arithmetic. What do you get for the product of PV? When you divided that by R what do you get? When you divide that by the number of moles, what do you get?

  6. Dec 9, 2014 #5
    So I did (3.60)(81.37)/(1.15)(0.08206) into my calculator in order to get T in Kelvins.
  7. Dec 9, 2014 #6
    Yes. That's correct. When I did it on my calculator, I got 3104K. That 0.08206 is in the denominator, not in the numerator. You need to be careful with your parenthesis.

  8. Dec 9, 2014 #7


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    I guess the temperature wasn't in the 200s after all. The surface of the sun is about 5700 K, so this gas sample is quite the hot potato.
  9. Dec 9, 2014 #8
    Ha!! I noticed that. That's what I get for trying to do it in my head.

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