van der Waals Phase Behavior

[@annfanzheng7317]

Thank you so much for the video. I am learning thermaldynamics in uni now, but you explained the concepts so much better than my prof for this module.

[@PhysicalChemistry]

Thanks for the comment, that's very kind of you

[@ollliveira]

That was a piece of art! Many thanks!

[@PhysicalChemistry]

Thanks! I'm glad you liked it

[@roshanpatel4037]

I like how you emphasize the limitations of the cubic form of the VDW model. The origin of this unphysical behavior was always unclear to me, but emphasizing that it is indeed an artifact of the model is helpful in understanding the big picture. Thank you.

[@PhysicalChemistry]

Yes, there is so much attention paid to the phase loops of the vdW isotherms that it can be easy to lose track of the fact that they're just a model artifact not something real.

[@eduardohollauer6346]

Dear dr stuart ! Very good talk ! I apologize for a small mistake ! In the cubic expression the correct second term is _(b+RT/p) and not (-b+RT/P) ! I hope you migth check your transparencies !

[@PhysicalChemistry]

You're absolutely correct, thanks for pointing out that mistake. The equation is correct in the vdW Equation of State video (kzbin.info/www/bejne/sGjQioeYoJhsZ7c), but I wrote the sign wrong here, as you pointed out. I'll pin your comment so that other viewers hopefully see the correction, and will work on editing / re-recording this one.

[@Khalid-hb7qb]

Your videos are amazing, and very beneficial. this is the second time you help me to understand a concept. Thank you.

[@PhysicalChemistry]

Well, then I'm doubly pleased to have been of service.

[@unlisted5685]

This answered my question you're the best Prof

[@PhysicalChemistry]

Thanks, glad to hear it

[@Kapish_]

Thanks a lot! This is the exact graphical explanation that I was looking for!

[@PhysicalChemistry]

You're welcome, glad to help

[@hakeemnaa]

this video is a masterpiece i dont know how to think you for this great explaining

[@PhysicalChemistry]

No thanks are necessary, but I appreciate your kind comment

[@xursssulaxx]

can you please explain the equal area theorem and how to iterate psat values at different temperatures to find the volume of the vapor and liquid phases? (binodal points?) i have been trying to figure it out but can’t

[@PhysicalChemistry]

The basic idea is: Pick a P_sat. Find the roots V(P,T) that solve the vdW equation. There will be 3 of them if you are in the coexistence region. Then obtain the areas of the two phase loops: ∫P(V) dV from V₁ to V₂ and from V₂ to V₃. At the correct P_sat, these areas will be equal. You can change your guessed value of P_sat until this equal-area condition is met.

[@hugoscoviske]

What a concise explanation! One of the best ways I've ever seen to approach such a hard topic. Do you recommend any specific Physical Chemistry/Themodynamics book for those who wants to study on their own? Thank you so much, professor Stuart!

[@PhysicalChemistry]

Thanks! If you're happy with a quantum-first presentation of topics, then the book by McQuarrie and Simon is quite good, and certainly suitable for self-study. Unfortunately, I don't know of a great book that follows the Boltzmann-first order of topics that I present here. I'm working on one of my own, but it is not available just yet.

[@saracareaga7539]

One Question the derivative of the pressure with respect to the volume at constant temperature shouldn't be equal to -1/VK?

[@maxmartin8470]

Are you writing backwards since you're on the other side of the glass?

[@PhysicalChemistry]

I am on the other side of the glass, but I'm writing forwards! The computer reverses the image. More details: kzbin.info/www/bejne/j57Ze4mhrq-VgsU

[@JyotiYadav-zq9vc]

Sir, Even after the video I am unable to understand the decrease in volume with decrease in pressure Can only a cubic equation sufficient to for the unrealistic curve Or it is right to say that van der waal equation is not completely correct, even not the Berthelot and Dietrici

[@Amr-iu6wv]

Thank you a lot ❤

[@PhysicalChemistry]

My pleasure

[@franciscoresende4476]

👌