Langmuir-Hinshelwood Kinetics: Summary
The answers to the ConcepTests are given below and will open in a separate window.
Key points from this module:
- When one reactant strongly adsorbs, increasing the concentration of that reactant can decrease the reaction rate because less of the other reactant is able to adsorb. That is, the reaction rate can appear to have negative order with respect to that reactant.
- If a product is sufficiently weakly adsorbed, its concentration can be ignored in the denominator of the L-H rate expression.
- For a Langmuir-Hinshelwood mechanism, adsorption, desorption, or surface reaction can be rate-limiting.
- The apparent activation energy for a catalytic reaction can depend on the surface reaction activation energy and heats of adsorption of reactants and/or products.
From studying this module, you should now be able to:
- Derive the rate law for a Langmuir-Hinshelwood mechanism where adsorption, surface reaction, or desorption is the rate limiting step.
- Predict how reaction rates change with reactant concentrations for Langmuir-Hinshelwood kinetics.
- Determine the apparent activation energy for a catalytic reaction when certain assumptions are made.
Prepared by Nathan Jarvey and John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder