Physical Chemistry/State Functions

The following demonstrates what's a state function and what's not a state function. is not exact differential for a gas obeying van der Waals' equation, but is as demonstrated below: We assume quasistatic situation, so . Now, you take the cross partial derivatives. They are not equal; hence, is not exact differential (not a state function). However, if we take it will be exact differential (a state function). Take the cross partial derivatives. Both are equal making exact differential (a state function). fr:Chimie physique/Fonction d'état