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Find entropy change for free expantion of ideal gas

  1. Oct 11, 2012 #1
    entropy = jouls/kelvin
    supose 1 liter of ideal gas is allowed to freely expand into a 2 liter volume in an isolated system
    the energy in the system would remain the same,
    the temperature in the system would remain the same
    therefore if entropy =jouls/kelvin the entropy would remain the same
    howerer if 1 liter of ideal gas is allowed to freely expand into a 2 liter volume in an isolated system the entropy does increase.
    how dose entropy=jouls/kelvin ?
     
  2. jcsd
  3. Oct 12, 2012 #2

    Andrew Mason

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    ΔS = ∫dS = ∫dQ/T over a reversible path between the initial and final states.

    The initial state is (P,V,T) and the final state is (P/2,2V,T). So to calculate the entropy change you have to find a reversible path between those two states. (hint: the reversible path involves work being done and heat flow into the gas).

    AM
     
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