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Homework Help: Ideal Gas Law and pressure in a holder

  1. Feb 18, 2012 #1
    1. The problem statement, all variables and given/known data
    What is the pressure inside a $50.0$ L container holding $105.0$ kg of argon gas at $20^\circ$ C?

    2. Relevant equations
    Ideal Gas Law: PV=nRT

    3. The attempt at a solution
    From the ideal gas law, I get
    P=\frac{nRT}{V}=\frac{\frac{105.0\times 10^3g}{36g/mol}\times 0.08214\frac{L\cdot atm}{mol\cdot K}\times 293^\circ K}{50.0 L}=25258atm
    which seems much too large. Am I doing something wrong?
    Last edited: Feb 18, 2012
  2. jcsd
  3. Feb 18, 2012 #2
    Nope! Your answer is quite reasonable, and it seems like nothing looks wrong in your setup of P= nRT/V and all the units match, your value for R is correct and you've converted C to K. Unless you made a calculating mistake, everything looks correct to me.
  4. Feb 18, 2012 #3
    Oh wow, thanks! It's hard to believe the massive pressure inside, which was why I was skeptical. Thanks again.
  5. Feb 18, 2012 #4
    On second glance, your molar mass for Argon seems to be off, also, you've made a calculation error. Try again and tell me what you got. (I've worked it out this time).
  6. Feb 18, 2012 #5
    Oh, should it be [itex]39.95\times 2[/itex] since it's diatomic?
  7. Feb 18, 2012 #6
    Nono, on the work you've showed in your original post, it looks like you've put 36 g/mol.
  8. Feb 18, 2012 #7
    But the molecular mass of Argon is 39.95 isn't it? I'm just substituting the 36 for 39.95x2.
  9. Feb 18, 2012 #8
    By looking at the problem you've presented it should look like this:

    P = [(105000/39.95)(0.08214)(293)]/(50)
    P = 1265.1 atm
    P = 1.27 x 10^3 atm

    I've left out the units for simplicity, but you should write them in yourself.
  10. Feb 18, 2012 #9
    Oh, yeah. For some reason I thought argon was diatomic...
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