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Maintaining constant pressure of a gas

  1. Jul 6, 2011 #1
    i have a rather silly question involving PV = nRT and Charles's Law.
    Charles's Law states that the volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas.

    I'm wondering about how do you maintain a constant pressure of the gas?... because when you increase the temperature, the pressure of the gas also wants to increase because the molecules have more kinetic energy.

    How, in general, do you maintain constant pressure of a gas?
     
  2. jcsd
  3. Jul 6, 2011 #2

    Ygggdrasil

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    You can maintain a constant pressure on the gas by putting it into a container that is free to expand/contract. This way the pressure of the gas will always be equal to the external atmospheric pressure. If the pressure inside the container is higher than the atmospheric pressure, there will be a net force pushing out against the walls causing the container to expand which will reduce the pressure of the gas inside the container. Similarly, if the pressure inside the container is lower than the atmospheric pressure, there will be a net force pushing inward against the walls of the container causing the container to contract and increasing the pressure of the gas inside the container.
     
  4. Jul 6, 2011 #3
    perfect explanation! thanks so much!
     
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