Dave writes:

And the significance of this distinction between Chemistry and
thermodynamics is ...

The study of physics involving temperature, pressure, heat, work, etc., is
called "thermodynamics". Chemistry as such does not answer such questions,
although chemists use thermodynamics.

It is kind of like the old quarrel over whether chemistry is a branch of
physics, or physics of chemistry.

In any case, PV = nRT presumes zero heat transfer (denoted Q in
thermodynamics).