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Homework Help: Ideal Gas Law and kinetic energy

  1. Nov 13, 2008 #1
    1. The problem statement, all variables and given/known data
    An empty room in a house near the Atlantic coast has a volume of 45m3. What is the kinetic energy of all of the gas molecules in the room on a 30C summer day?

    2. Relevant equations
    pv = nrt

    3. The attempt at a solution
    I realize that this is an ideal gas law problem, but I have no idea where to start. How can I solve for anything if I'm only given volume and temperature?
  2. jcsd
  3. Nov 13, 2008 #2


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    Homework Helper

    You are on the right track. Maybe start here?
  4. Nov 13, 2008 #3
    Okay, so I use the equation PV = (2/3)K. I assumed that the pressure is the standard 1 atm. Plugging everything into the equation:

    101300 Pa (45 m3) = (2/3)K
    K = 6837750 J

    But the computer is telling me that this is the wrong answer. Did I do something wrong?
  5. Nov 13, 2008 #4


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    Homework Helper

    I think perhaps you want to use the relationship that KE = 3/2*k*T
    That gives you the KE per particle and you can figure the number of particles from the Volume at 30° C = 303° K.
    The k here is Boltzmann's constant 1.38 *10-23 J/°K

    Noting that the volume of air occupied by 1000 moles of air is given here:

    With 41 (1000/24.466) moles of air per m3 *45 m3 ... then you should be able to figure the total KE for that many moles of air in a 45 m3 room.
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