Chapter 18, Problem 18.105SP

(a)

Interpretation Introduction

Interpretation:

Molar heat of vaporization of benzene has to be determined.

Concept Introduction:

According to Trouton’s rule, ratio of molar heat of vaporization of a certain liquid to its boiling point $\left(inK\right)$ is around $\text{90 J/K}$.

Molar enthalpy of vaporization is the amount of energy required to convert one mole of a particular substance from solid to gas.

(b)

Interpretation Introduction

Interpretation:

Vapor pressure of benzene at $74°C$ has to be calculated

Concept Introduction:

Clausius-Clapeyron equation:

$\text{ln}\text{P}\text{=}-\left(\frac{{\text{Δ}}_{\text{vap}}{\text{H}}_{\text{0}}}{\text{RT}}\right)\text{+}\text{C}$

From this relationship we can calculate the molar enthalpy of vaporization by knowing the corresponding temperature and pressure values.

If we have pressures at two different temperatures, then enthalpy of vaporization can be calculated by

$\text{ln}\frac{{\text{P}}_{\text{2}}}{{\text{p}}_{\text{1}}}\text{=}\text{-}\frac{{\text{Δ}}_{\text{vap}}{\text{H}}_{\text{0}}}{\text{R}}\left[\frac{\text{1}}{{\text{T}}_{\text{2}}}\text{-}\frac{\text{1}}{{\text{T}}_{\text{1}}}\right]$