You have learned that phase changes are isothermal processes, yet a certain amount of heat is absorbed or gained by a substance as it undergoes phase changes. Using Thermodynamic data provided in appendix L and the following data:
MP: -97.8°C
BP: 64.7°C
C(l) 2.53 J/g•K
C(g) 1.38 J/g•K
-ΔfusH°: 2.196 kJ/mol
a. Calculate the enthalpy changes as methanol’s temperature is raised from -100°C to 80°C.
b. With your calculated sketch an accurate heating curve for methanol.
c. Calculate the ΔS°sys, along your heating curve and sketch an accurate entropy vs. temperature curve.
d. Calculate the ΔSuniv, and ΔG° for the conversion of 2.00 L of liquid methanol to gaseous methanol.
e. What do your calculated values for ΔSuniv and ΔG° tell you about the spontaneity of this process.
f. Using the equation of your choice, determine and illustrate under what conditions the condensation of methanol is spontaneous.
g. If the ΔvapH° and ΔfusH° are exothermic, why are these processes isothermal and spontaneous under certain conditions; where is the heat going?
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