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

1. Apr 28, 2013

### doombanana

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

$\frac{dP}{dT} = \frac{L}{T(v^{(f)}-V^{(i)})}$

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. Apr 29, 2013

### Staff: Mentor

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?