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Calculate latent heat

  1. Jan 3, 2009 #1

    KFC

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    We could use the change of entropy before and after eh phase changed to calculate the latent heat

    [tex]
    L = (S_{after} - S_{before})T
    [/tex]

    and in some case, if we know the relation of pressure and temperature, we can also apply Clausius-Clapeyron relation to calculate the latent heat.

    I wonder if there is any usual way to calculate the latent heat for phase change. If the pressure is unchanged we see that then change of enthalpy is same the

    [tex]\Delta H= T\Delta S[/tex]

    So can I say the latent heat of phase change b/w any two phase for any system is equal to the change of enthalpy of this system during the phase change?
     
    Last edited: Jan 3, 2009
  2. jcsd
  3. Jan 4, 2009 #2

    olgranpappy

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    Homework Helper

    Yes, it's okay since the transition occurs at constant temperature and pressure.

    [tex]
    L\equiv\Delta Q = T\Delta S=\Delta H - V\Delta P=\Delta H\;.
    [/tex]
     
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