Question

Consider the following liquid - vapour equilibrium Liquid $\rightleftharpoons$ Vapour. Which of the following relations is correct?

• A. $\frac{dlnG}{d{T}^2}=\frac{\Delta H_v}{R{T}^2}$
• B. $\frac{dlnP}{dT}=\frac{-\Delta H_v}{RT}$
• C. $\frac{dlnP}{d{T}^2}=\frac{-\Delta H_v}{T^2}$
• D. $\frac{dlnP}{dT}=\frac{\Delta H_v}{R{T}^2}$

Answer 1

The correct option is D $\frac{dlnP}{dT}=\frac{\Delta H_v}{R{T}^2}$

According to Clausius - Clapeyron's equation

$\frac{dlnP}{dT}=\frac{\Delta H_v}{R{T}^2}$

According to this equation, the rate at which the natural logarithm of the vapor pressure of a liquid changes with temperature is determined by the molar enthalpy of vaporization of the liquid, the ideal gas constant, and the temperature of the system.