- #1
Big-Daddy
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On a (T,P) phase diagram, what is meant by the pressure at each phase for the substance? Chemically speaking we are only usually dealing with "gaseous" pressure (i.e. that exerted by the gases), but only when the substance is in (one of the phases in) the gaseous state or supercritical fluid state will it exert gaseous pressure, so what is meant by the value of P for the substance when in a phase that is not gaseous (or supercritical)? Perhaps, the surrounding gaseous pressure?