Adsorption constants are equilibrium constants, therefore they obey the Van 't Hoff equation:
As can be seen in the formula, the variation of K must be isosteric, that is, at constant coverage.
If we start from the BET isotherm and assume that the entropy change is the same for liquefaction and adsorption, we obtain
that is to say, adsorption is more exothermic than liquefaction.