I'm a first timer here. In a normal liquid-vapor P-V biphasic curve at a temperature below critical temperature, we can compress a vapor at a constant temperature till it becomes saturated, or is just about to turn into a liquid. Any further compression would lead to the existence of the two phases together, as we know. Here we can see from the phase rule that we have just one degree of freedom. So just specifying the temperature will set the pressure and volume, just like what the Antoine equation gives.
A pre-question here is that once we come into the zone inside the bell curve of mutual phase existence, what does the volume in the X-axis specify? (Like volume of the gas or volume of the liquid)
My main question is once it enters this zone where the temperature and pressure are set at a saturated value, what is the driving force for the conversion of the vapor to liquid. By this I mean, how can we ensure that two distinct desired compositions can be achieved if we perform the experiment two different times. Surely this isn't to be a transient process where the end result is always full saturated water. I would really appreciate if someone could clear this for me. I have tried looking everywhere for an answer to this, and I did not find it here either. Pardon me if I didn't look enough here.