While reading about the Clausius Clapeyron equation from the Feynman lectures on Physics, I couldn't understand a few things from its derivation:
Although the argument was pretty clear, when the system consists both gas(vapour) and liquid why would it have constant pressure on heating and increasing volume??
Second and more fundamental, how can we assign a single pressure value to this composite system in spite of it having two states of matter; wouldnt the pressure in the gas part (on top part of container) be different from that at the bottom or side in the liquid part? On top of this how can this be the vapour pressure (which I think is the pressure of the vapours on the surface of liquid)?