Langmuir Adsorption Isotherm
A model describing monolayer adsorption on a surface with a fixed number of equivalent, independent sites.
Formula / equation
θ = Kp / (1 + Kp)
Unit
Dimensionless
In depth
The model assumes that all sites are identical, that each holds one molecule, and that adsorbed molecules do not interact. Surface coverage rises linearly at low pressure and saturates at high pressure, which explains why many surface-catalysed reactions shift from first to zero order.
Examples in the real world
The zero-order decomposition of HI on gold at high pressure, where the surface is fully covered.