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Homework Help: Temperature dependence of a latent heat.

  1. Jan 15, 2008 #1
    1. The problem statement, all variables and given/known data
    You Need to find the enthalpy of sublimation of solid A at 300K. The following equilibrium vapor pressure measurements have been made of pure A : (1) At 250K, the pressure is 0.258 bar and (2) At 350K, the pressure is 2.00 bar. The following heat capacity data is known:
    Cp(solid) = 40 J/(mol K) ; Cp(vapor) = 40 + 0.1*T J/(mol K)

    Calculate the enthalpy of sublimation, accounting for the temperature variation of the enthalpy of sublimation.

    2. Relevant equations

    Claussius-Clapeyron Eqtn: dP/P = ((delta H sublimation) / R) * (dT / T^2)
    Change in Enthalpy (Ideal) = integral (Cp * dT)

    3. The attempt at a solution

    None. I cannot think of a way of including the temperature dependence of the heat of sublimation.
  2. jcsd
  3. Mar 21, 2009 #2
    OK the simplest way to interpolate is linear interpolation, and in this way I find equilibrium vapor pressure of 1,229 Bar.
    How do I get enthalpy from this?
    greetings Janm
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