BET Theory?

[manicmajor]

I tried looking up information regarding the BET Theory (http://en.wikipedia.org/wiki/BET_theory), but I was unable to find anything related to assumptions made from the BET Theory.

 

Background: I'm doing a lab report on physical adsorption. A discussion question asks "Consider each of the five assumptions inherent to BET theory..."

 

I understand the equation as listed in Wikipedia, but would anyone know assumptions that were made or can be pulled from the equation?

[encipher]

I think i can recall a few:

 

1. That the adsorbed molecules stay put

2. That the energy of absorbtion is the same for all layers except the first.

3. That the enthalpy of adsorbtion is the same for all the layers.

 

 

If i remember any others Ill post.

[manicmajor]

That was what I was trying to figure out

[encipher]

I don't quite recall the fourth.. i beleive there are only 4... not 5. At least i dont remember a fifth. Anyways the forth has to do with the formation of layers.. but i dont remember. Should've paid more attention in class =\

[encipher]

Well, I found this in a document on UFL's site:

 

The B.E.T. theory is based on several assumptions:

 

i) adsorbent consists of a regular array of adsorption sites equal in energy, with a constant enthalpy of adsorption in the monolayer, DHA

ii) adsorption is localised to these sites

iii) neighbouring adsorbed molecules do not interact

iv) multilayer formation is unlimited

v) enthalpy of adsorption in second and subsequent multilayers is equal to the enthalpy of liquefaction, DHL

vi) adsorption or desorption may only occur on or from exposed sites.

[manicmajor]

What is UFL?

[encipher]

University of Florida . (actually it wasnt ufl.. wasnt wearing my glasses)

 

here's the URL:

 

http://www.staff.ncl.ac.uk/a.j.fletcher/isotherms.htm