Activation Energy and Catalysts Unit 4: Kinetics Activation Energy and Catalysts

Activation Energy Minimum amount of energy for reaction to occur during a collision

Reaction Coordinate Diagram Reaction coordinate diagrams show the energy changes throughout the reaction Activated complex (Also called the transition state) Activation Energy Products Energy Energy change for reaction Reactants Reaction proceeds

Activated Complex What is an “activated complex”? F N O N O F F Reaction proceeds Energy Activated Complex Reactants F2NO2 F2 + NO2 Products F + FNO2 F N O N O F F

Catalysts Catalysts – Substance that increases the rate of reaction without being used up A + B + C  D + C “C” is the catalyst…it is present in the beginning and in the end Enzymes are catalysts in the body

Catalysts & Reaction Diagrams Reaction Path without catalyst Reaction Path with catalyst Energy Reaction proceeds Catalysts lower the activation energy of the reaction by letting it proceed in a different way. With lower activation energy, a higher percentage of collisions will be successful (they don’t need to collide with as much energy to be successful)

Catalysts How do catalysts help speed up the reaction without being used? They increase the chances that a collision will successfully produce a reaction For example, catalysts hold one or more of the reactants in place to allow collisions to occur with the correct orientation Catalysts make a successful collision more likely. They lower the activation energy by allowing reactants to react in a different way, or by holding reactants in place for the reaction. Once they’ve done their job, they are released and available to “help” another reactant. Once the reaction has occurred, the catalyst releases the molecule(s) and finds another one to help