The Langmuir Adsorption Isotherm: Derivation and Its Limits
Physical Chemistry · Surface The Langmuir Adsorption Isotherm: Derivation and Its Limits The derivation is short, the assumptions are strong, and questions test the assumptions at least as often as the equation. BSc & MSc · Physical Chemistry · Concept The short answer: Set the rate of adsorption equal to the rate of desorption at equilibrium and solve for the fraction of surface covered. The result is θ = Kp/(1 + Kp). It assumes a monolayer, identical sites and no interaction between adsorbed molecules — and each of those assumptions is where the model fails. The assumptions, stated first These…