In Langmuir's model of adsorption of a gas on a solid surface
the adsorption at a single site on the surface may involve multiple molecules at the same time.
the mass of gas striking a given area of surface is proportional to the pressure of the gas.
the mass of gas striking a given area of surface is independent of the pressure of the gas.
the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered.