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Homework Help: Ideal Gas Equation

  1. Aug 26, 2010 #1
    1. The problem statement, all variables and given/known data

    The ideal gas equation, PV=nRT, may have the following units:
    P is given in bar (bar)
    V is given in m3 (cubic meters)
    N is given in mol (moles)
    T is given in K (kelvin)

    Which value of R would you use for the calculation if you were using the above units for the other variables in the calculation?

    2. Relevant equations

    Dont have any.

    3. The attempt at a solution

    I have no attempt at the solution as i honestly do not understand how to come to a conclusion. I am a first year university student, having just started a degree in Biochemistry - and i have three basic chemistry modules to complete before i can get onto Biochemistry.

    This being a career change for me at age 34, and not having done science in school, i am really stuck and have been battling on this question for a week now.

    Any help would be greatly appreciated - just an explanation of where to start would be of great help.

    Thanks!
     
  2. jcsd
  3. Aug 26, 2010 #2

    Borek

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    Staff: Mentor

    Solve for R - and replace given symbols (P, V, n, T) with units.

    --
    methods
     
  4. Aug 26, 2010 #3
    The gas constant's value is determined by its units. If you alter the units you need to alter the value of the constant also. The gas constant is joules per (kelvin x mol). If you multiply pressure in pascals by volume in metres you get joules. Since your volume is in metres already, you need to find out the relationship between pascals and bar.
    At least, I think thats correct...
     
  5. Aug 26, 2010 #4
    You beat me Borek!
    Is what I said reliable?
     
  6. Aug 26, 2010 #5

    Borek

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    Staff: Mentor

  7. Aug 26, 2010 #6
    Thank you for the response :)

    Problem is - the question is exactly as i typed it. There are no units given, at all. Hence why i am stumped :/

    Have they perhaps made a mistake, or am i really being clueless?
     
  8. Aug 26, 2010 #7

    Borek

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    Staff: Mentor

    No units?

    --
    methods
     
  9. Aug 26, 2010 #8
  10. Aug 26, 2010 #9
    You could start with [tex]R = 0.0821 \frac{L\cdot atm}{mol\cdot K}[/tex] and convert the pressure and volume to the other units.
     
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