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Homework Help: Amount of CO2 vaporized in a phase change from liquid to solid & vapor

  1. Apr 28, 2013 #1
    1. The problem statement, all variables and given/known data

    Saturated liquid CO2 is at T= 293 K and P=5.72*10^6 Pa and undergoes throttling to P=1.01*10^5. The resulting solid and vapor mixture is at T = 195 K. What fraction of the carbon dioxide is vaporized? (The enthalpy of the saturated liquid in the initial state is 24,200 J/mol, and the enthalpy of the saturated solid in the final state is 6750 J/mol. The heat of sublimation at the final temperature and pressure is 25,100 J/mol.)

    2. Relevant equations

    [itex] \frac{dP}{dT} = \frac{L}{T(v^{(f)}-V^{(i)})} [/itex]

    3. The attempt at a solution

    I am really unsure of how to go about this problem. Using the equation above, I can find expressions for vaporization, sublimation, and freezing, but I don't know the heat of vaporization or any of the initial or final volumes. Any help would be greatly appreciated.
  2. jcsd
  3. Apr 29, 2013 #2
    What is the change in enthalpy during a throttling operation? If the enthalpy of the solid in the final state is 6750 J/mole, and the heat of sublimation under the final state conditions is 25100 J/mole, what is the enthalpy of the final vapor in J/mole?
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