C.2 Shown is a portion of the phase diagram for CO2. 10 CO2 Liquid 8 Pressure (bar) Solid 2 Gas 0 -80 -70 -60 -50 -40 -30 Temperature (C) In a simplified model for solid CO2 (dry ice), CO, molecules are spheres arranged in a face centred cubic structure, interacting with neighbours through a Lennard-Jones pair potential Upair = 48 [9)"- (9)"] where o = 3.6 A and € = 0.044 eV.
The Clausius-Clapeyron equation is given as dp L dT TAV where dp/dT is the slope of the phase boundary at pressure p and temperature T, AV is the difference in volume between phases at p and T, and L is the latent heat of transfor- mation. You may assume 1 bar = 10 Pa. At ambient pressure, calculate the change in molar volume upon vapourisation in CO2 By what factor does the volume increase upon vapourisation at ambient pressure? Evaluate your answer for plausibility.
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