Chapter 12, Problem 12.23P

Interpretation Introduction

Interpretation:

$\Delta H_{\text{vap}}^{°}$ of a liquid that has a vapor pressure of $621\text{ torr}$ at $85.2°\text{C}$ is to be calculated.

Concept introduction:

Clausius-Clapeyron equation is used to find the vapor pressure at one temperature when vapor pressure at another temperature and heat of enthalpy is given. It determines the change in vapor pressure with a change in temperature. The expression of the Clausius-Clapeyron equation is as follows:

$\ln \left(\frac{P_2}{P_1}\right)=\frac{-\Delta H_{\text{vap}}}{R}\left(\frac{1}{T_2}-\frac{1}{T_1}\right)$ (1)

Here,

$P_1\text{ and }{P}_2$ are the vapor pressure.

$T_1\text{ and }{T}_2$ are the temperature.

$R$ is the gas constant.

$\Delta H_{\text{vap}}$ is the heat of vaporization.

The conversion factor to convert $°\text{C}$ to Kelvin is as follows:

$T\left(\text{K}\right)=T\left(°\text{C}\right)+273$ (2)

The conversion factor to convert $\text{atm}$ to $\text{torr}$ is as follows:

$1\text{atm}=760\text{torr}$ (3)