So though this is written in a physics format. I suspect this relevant for metrology but still wanted a second opinion if this question would be welcome here?
To me Physics SE was a good fit, much better than here. Sure, here you'll find some physicists with good knowledge of gas mixing equations and such, but applied to atmospheric science problems. As it is written now, your question is purely theoretical, with absolutely no link to any earth science system. It would probably be considered off-topic. From the help center:
Earth Science Stack Exchange is for questions related to earth science disciplines. [...] If your question is not specifically on-topic for Earth Science Stack Exchange, it may be on topic for another Stack Exchange site (e.g. Physics, Chemistry).