Hertz–Knudsen equation
The Hertz–Knudsen equation, also called the Knudsen–Langmuir equation, is a simple result in surface chemistry. It describes how many gas molecules hit a surface each second per unit area, and how this rate depends on the gas pressure, temperature, and the properties of the gas molecules and the surface. It applies to non-dissociative adsorption, where a molecule lands on the surface and sticks without breaking apart. Because the rate comes out in units of per second per area, it can be used as a rate constant for the adsorption process (when you account for the probability that a molecule actually sticks to the surface).
This page was last edited on 2 February 2026, at 15:08 (CET).