Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rate of ideal gas expansion

  1. Oct 11, 2004 #1
    can anyone give me an equation for the rate that an ideal gas expands in a temperature change. like when a gas goes from 30 degrees to 50 degrees in a baloon. how quickly would it expand?
     
  2. jcsd
  3. Oct 11, 2004 #2

    mrjeffy321

    User Avatar
    Science Advisor

    you need to use the ideal gas law to figure it out.
    Let P be the pressure of a gas, V the volume it occupies, and T its temperature (which must be in absolute temperature units, i.e., in Kelvin). Then the ideal gas law states

    PV = nRT


    where n is the number of moles of gas present and R is the universal gas constant, or equivalently


    it would expand to the new volume as the gas temperature inccreases, there isnt a real amount of time it takes to expand, it just expands as the temperature increases. if the temperature were to suddenly increase by 20 degrees, then the gas would suddenly expand to the the new volume, but normaly it would be a gradual process because the temperture increasing is a gradual process.
     
  4. Oct 12, 2004 #3

    movies

    User Avatar
    Science Advisor

    Well, the ideal gas law is only valid for static systems, right? So I guess the answer would be that it would take as long as was needed for the system to re-equilibrate at the new parameters.
     
  5. Oct 12, 2004 #4

    chem_tr

    User Avatar
    Science Advisor
    Gold Member

    Maybe you can try to use diffusion alternative... Diffusion rate changes in an indirectly proportional way with the molecular mass.
     
  6. Oct 12, 2004 #5
    It seems to me that you would have to take the partial derivative of Volume with respect to T so you would get dV/DT=nR/P. So if pressure and amount of gas is held constant, the rate at which it expands is constant.
     
    Last edited: Oct 12, 2004
  7. Oct 12, 2004 #6
    This is basically the same thing that Guy-Lussac's law says. V=kT where k is some constant. So for example, if T doubles then volume will double (only if pressure and the amount of gas is held constant). Writing dV/dT=nR/P is just a more "sophisticated" way of stating the same thing.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Rate of ideal gas expansion
  1. Ideal gas probs (Replies: 3)

  2. Un-ideal Gas Equation! (Replies: 1)

  3. Non-ideal gas? (Replies: 1)

Loading...