Octane has a vapor pressure of 40. torr at 45.1$\degree$C and 400. torr at 104.0$\degree$C. What is its heat of vaporization?
A) 39.0 kJ/mol
B) 46.0 kJ/mol
C) 590 kJ/mol
D) 710 kJ/mol
E) None of these choices is correct.

Question

Quizplus · Accepted Answer

Clausius-Clapeyron equation:$$\ln\frac{P_2}{P_1}=\frac{\Delta H_{vap}}{R}(\frac{1}{T_1}-\frac{1}{T_2})$$$$\Delta H_{vap}=R(\frac{T_1T_2}{T_2-T_1})\ln\frac{P_2}{P_1}$$$$=(8.314\frac{J}{mol\cdot K})(\frac{(45.1+273.15)K(104.0+273.15)K}{104.0K-45.1K})\ln\frac{400.torr}{40.torr}$$$$=39.0kJ/mol$$

Octane Has a Vapor Pressure of 40 °\degree° C and 400 Torr at 104

Octane Has a Vapor Pressure of 40 $\degree$ C and 400 Torr at 104