Final answer:
The BET equation is primarily associated with multilayer adsorption and is most accurate in the monolayer range. It extends the Langmuir model, which is limited to monolayer adsorption, to include multilayer formation up to a liquid-like film.
Step-by-step explanation:
The question addresses whether the Brunauer-Emmett-Teller (BET) equation is applicable only to the monolayer adsorption range.
The BET theory is widely used to analyze adsorption data and is predicated on the concept of multilayer adsorption. It extends beyond just monolayer coverage to model multilayer adsorption up to the point of forming a complete multilayer film that behaves like a liquid.
However, it is most accurate in the range where monolayer adsorption occurs, and as it approaches higher pressures, the assumptions of the BET model become less valid, leading to deviations.