Question

1. The normal boiling point of benzene (i.e., at 1 atm) is 80.09 °C. The molar enthalpy of vaporization is 30.72 kJ mol . Assuming that AvapHm and AvapSm stay constant at their values at 80.09°C, calculate the values of AvapGm at 75.0 °C, 80.09 °C and 85.0 °C. Given your calculated values, do you still expect benzene to spontaneously condense at 75.0 °C and to spontaneously evaporate at 85.0°C? -1 2. The vapor pressure of a liquid was measured from 200 K to 260 K and found to fit the expression Ln(P) 18.361- 3036.8 T. (P was measured in torr and T in K.) Find the enthalpy of vaporization of the liquid. 3. The boiling point of a certain liquid is 24.1 C at a pressure of 400 torr. Its enthalpy of vaporization is 28.7 kJ/mol. What is its boiling point at a pressure of 500 torr? 4. You have synthesized a compound that has a negative enthalpy of vaporization. In other respects it is normal: its enthalpies of fusion and sublimation are positive, and the density of the liquid is less than that of the solid and more than that of the gas. Sketch a phase diagram for this compound that is consistent with these observations.

Answer 1