vdW Equation of State (Molar Volume)

Solving for the volume of a gas using the van der Waals equation of state is not as straightforward as solving for the pressure.

[@damianezell5021]

This video was super helpful! Needed a refresher on Van der Waals and this lined up perfectly with what I needed! You’re a life saver

[@PhysicalChemistry]

Happy to help

[@abdulz2]

It’s a great lecture and I’m revising my physics chemistry knowledge, so many things are clearer than ever! Coming to my question, what is the pressure and temperature cut off value for a real gas to stay in ideal condition, since ideal gas conditions says only low pressure and high temperature?

[@stevenjstuart]

There's no specific cutoff. For one thing, the ideal gas law is *always* wrong. The cutoff you're looking for would just depend on whether you're okay with errors of 1% or 0.1% or 0.01% or ... For another, the cutoff would be different for every gas. At a given T and P, nitrogen behaves more ideally than steam.

[@abdulz2]

@@stevenjstuart thank you so much for your replay, and I also got some of the things when I was looking at the following lectures.

[@zulqarnainchaughtai]

Below Tc we get three values for volume. McQuarrie book's says we can think of one volume for liquid one for gas and 3rd one is spurious,, what's that mean in physical sense?

[@PhysicalChemistry]

The best answer is that you should *not* try to interpret that middle solution in a physical sense. The real phase diagram becomes horizontal in the liquid/gas coexistence region. The (smooth, continuous) vdW curve can't become perfectly flat over an extended range of volumes. So the vdW "phase loop" that includes the spurious middle solution is just the vdW curve staying as flat as it can manage. But the actual P(V) behavior in that phase loop is nonphysical, so you shouldn't trust the numerical values.

[@zulqarnainchaughtai]

@@PhysicalChemistry Thank you!

[@patelarpit1359]

Thank u so much sir From this lecture i really correlated the mathematical sense with chemistry

[@PhysicalChemistry]

You're very welcome. There is so much beautiful mathematics hiding under the surface in chemistry, if you look for it!

[@tj794f]

Transferred to Ohio State yet here I am watching these. The irony... Go Tigers!

[@Renat9453]

Thank you! Very helpful video

[@PhysicalChemistry]

You're welcome, glad to help

[@antoniocavalcante1707]

what kind of board is this ?

[@PhysicalChemistry]

It's called a lightboard. Here's some more info: kzbin.info/www/bejne/j57Ze4mhrq-VgsU