Benzene has a vapor pressure of 183 mm Hg at 40 degrees Celsius. Taking it's heat of vaporization to be 30.8 kJ/mol, calculate it's vapor pressure at 25 degrees Celsius. The answer is 101 mm Hg, but I keep getting 4.613, and I can't figure out where 101 mm Hg comes from.

Question

Benzene has a vapor pressure of 183 mm Hg at 40 degrees Celsius. Taking it's heat of vaporization to be 30.8 kJ/mol, calculate it's vapor pressure at 25 degrees Celsius. The answer is 101 mm Hg, but I keep getting 4.613, and I can't figure out where 101 mm Hg comes from.
ln 183-lnP1= 30.8 kJ/mol/8.31x10-3 ((1/298)-(1/313))
5.209-lnP1=0.596, therefore, ln P1 should equal 4.613.

DrBob222 · Answer

Thank you for showing your work.
You have done everything exactly right EXCEPT you have one more step to go through. Your answer is
ln p1 = 4.613.
Find the number for which ln p = 4.613 and it is about 100.7 which rounds to 101 mm. :-)