Physical chemistry
Surface adsorption
Adsorption accumulates molecules at a surface; Langmuir and BET models describe monolayer and multilayer uptake.
Distinguish surface adsorption from bulk absorption. Physisorption is mainly dispersive and often reversible; chemisorption forms more specific bonds.
Adsorption models
Adsorption accumulates molecules at a surface; Langmuir and BET models describe monolayer and multilayer uptake.
Definition: Core definition
Langmuir assumes equivalent, independent sites and one layer; BET extends the model to multilayer adsorption.
Example: Worked example
Apply the model to a simple case: As p rises, Langmuir approaches θ→1 as a monolayer saturates. BET uses adsorption near vapor saturation to estimate porous-material surface area.
Solution
As p rises, Langmuir approaches θ→1 as a monolayer saturates. BET uses adsorption near vapor saturation to estimate porous-material surface area.
Langmuir assumes equivalent, independent sites and one layer; BET extends the model to multilayer adsorption.
| Quantity | Model / rule |
|---|---|
| Key relation | Adsorption accumulates molecules at a surface; Langmuir and BET models describe monolayer and multilayer uptake. |
| Meaning / use | As p rises, Langmuir approaches θ→1 as a monolayer saturates. BET uses adsorption near vapor saturation to estimate porous-material surface area. |
What type of layer does ideal Langmuir adsorption assume?
Which statement best matches the model described?
References
- Stephen Brunauer (1945). Adsorption of Gases on Solids