General Chemistry Homework Question

Question

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 43.5 C.

Answer 1

Clausius-Clapeyron equation:

ln(P2/P1) = ∆Hvap/R (1/T1 - 1/T2)

P1 = 1 bar

P2 = ?

T1 = 56.1 + 273 = 329.1K

T2 = 43.5 + 273 = 316.5K

∆Hvap = 29.1 kJ/mole = 29,100 J/mole

R = 8.314 J/mol-K

ln(P2/1) = 29,100/8.314 (1/329.1 - 1/316.5)

ln P2 = 3500 (0.003039 - 0.003160)

ln P2 = 10.6 - 11.06 = -0.46

P2 = 0.63 bar