The standard (1 bar) boiling point of acetone is 56.1 C, and its enthalpy of vaporization is 29.1 kJ/mol. Calculate the vapor pressure of acetone at 41.7 C.

Answer 1

P1 = 1 bar

T1 = 56.1ºC + 273 = 329.1K

P2 = ?

T2 = 41.7ºC + 273 = 314.7K

∆Hvap = 29.1 kJ/mol

R = 8.314 J/Kmol = 0.008314 kJ/Kmol

Use the Clausius Clapeyron equation:

ln (P2/P1) = -∆Hvap/R (1/T2 - 1/T1)

ln (P2/1) = -29.1/0.008314 (1/314.7 - 1/329.1)

ln P2 = - 3500 (0.00318 - 0.00304)

ln P2 = -3500 (0.00014)

ln P2 = -0.49

P2 = 0.6 bar