# How can I calculate delta G of vaporization?

##### 1 Answer

Apr 26, 2017

All phase changes at constant temperature and pressure are in an equilibrium such that

The Gibbs' free energy for a closed system is a function of the temperature and pressure:

#G = G(T,P)#

*Even for an open system, the Gibbs' free energy is zero for any process in chemical equilibrium where the temperature and pressure are both constant.*

Any liquid that evaporates is in chemical equilibrium with itself, and is already at constant temperature (i.e. its boiling point!). At a constant altitude, we can safely assume that a constant pressure is in equilibrium with the atmospheric pressure (the condition for vaporization). Hence,