The vapor pressure of liquid chloroform,CHCl₃,is 400.0 torr at 24.1°C and 100.0 torr at -6.3°C.What is ΔH_vap of chloroform?

Question

Quizplus · Accepted Answer

The Clausius-Clapeyron equation relates the vapor pressure of a substance at different temperatures to its heat of vaporization ($\Delta H_{vap}$). The equation in its linear form is:$$\ln\left(\frac{P_2}{P_1}\right) = -\frac{\Delta H_{vap}}{R}\left(\frac{1}{T_2} - \frac{1}{T_1}\right)$$Given:- $P_1 = 400.0 \, \text{torr}$ at $T_1 = 24.1°C = 297.25 \, K$ (converting from °C to K by adding 273.15)- $P_2 = 100.0 \, \text{torr}$ at $T_2 = -6.3°C = 266.85 \, K$First, convert pressures to atmospheres because the gas constant $R$ is often given in units that are compatible with atmospheres:- $P_1 = 400.0 \, \text{torr} \times \frac{1 \, \text{atm}}{760 \, \text{torr}}$- $P_2 = 100.0 \, \text{torr} \times \frac{1 \, \text{atm}}{760 \, \text{torr}}$Then, plug the values into the Clausius-Clapeyron equation and solve for $\Delta H_{vap}$:$$\ln\left(\frac{100/760}{400/760}\right) = -\frac{\Delta H_{vap}}{8.3145 \, \text{J/mol·K}}\left(\frac{1}{266.85} - \frac{1}{297.25}\right)$$Solving for $\Delta H_{vap}$ gives a value close to 30.1 kJ/mol, indicating that option B is correct.

The Vapor Pressure of Liquid Chloroform,CHCl3,is 400

The Vapor Pressure of Liquid Chloroform,CHCl₃,is 400