Langmuir Adsorption - Limitations

[@rameshkalagnanam2946]

Prof. Stuart - you videos are absolutely a class of their own! You are a very effective teacher.

[@PhysicalChemistry]

I'm glad you thought so; thanks for the comments

[@artp0pa]

Please tell me, is it true, if my adsorption model is described with a high degree of correlation and the linearized form of the Langmuir equation (~R 2= 0.9592 for example) and the linearized form of the Freundlich equation (~R 2= 0.9892 for example), then I must say, that there are binding sites on the surface for both chemical and physical adsorption?

[@PhysicalChemistry]

No, that's not true. A purely physical adsorption prices could be described perfectly well by both Langmuir and Freundluch isotherms.

[@ishtierrahman71]

What is Toth Isotherm?

[@PhysicalChemistry]

That's another equation that can be used in the same way the Langmuir isotherm is used: to describe how the surface coverage (Θ) depends on the amount (pressure or concentrration) of unbound species. It is not used as widely as the Langmuir model. It has an extra (empirical) parameter, and can give more accurate results than the Langmuir model, and is perhaps used in some specialized fields. But the Langmuir (and BET) models are the ones we study at the introductory level because they can be derived theoretically, and they give more insight into the physical reasons for adsorption behavior.

[@ishtierrahman71]

@@PhysicalChemistry Thanks a lot for you kind reply. Can you also make some videos on Toth Isotherm? As you mentioned, and as far as my understanding, it is an extended version of Langmuir equation and I am finding it bit difficult to gather information about this process.

[@PhysicalChemistry]

@@ishtierrahman71 Sorry, I don't have plans for videos on any of the (many) other adsorption models.

[@mortezakhoshbin]

Thanks alot dear prof. if it is possible please tell about how that OH or H is bonded with surface which is metal or how could i know about this topic

[@PhysicalChemistry]

Several transition metals (and some oxides) act as catalysts for dissociation of water. So, at the surface of these metals, water can dissociate. When it does, the radicals are highly reactive, and bind to the metal surfaces. If you do a search for "water dissociation at metal surfaces", you can find plenty of journal articles with more details. You can even find a video or two, although they won't have as much detail: kzbin.info/www/bejne/e2KTfol_pc5lgck

[@mortezakhoshbin]

@@PhysicalChemistry Thanks alot🌹🌹🌹