Question

explain the important of using an equililrum process in development of the clausius clapeyron equation

Answer 1

Clausius-Clapeyron equation pertains to the relationship between the pressure and temperature for conditions of equilibrium between two phases. The two phases could be vapor and solid for sublimation or solid and liquid for melting.

The Clapeyron attempts to answer the question of what the shape of a two-phase coexistence line is. In the plane, we see the a function P(T), which gives us the dependence of P on T along a coexistence curve.

The importance of the quantity dPldt is that is represents the slope of the coexistence curve on the phase diagram between the two phases. Now, in equilibrium dG = 0, and since G = H – TS, it follows that dH = T dS at fixed T. In the narrow temperature range in which the two phases are in equilibrium, we can assume that H is independent of T , hence, we can write S = H/T. Consequently, we can write the molar entropy difference as ša – še = ""7" Ha - HB and the pressure derivative dPldt becomes dp Ēa - Hp AapH dT" TŪa - VB)TAMB]