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

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

3. 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

4. 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

5. 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

6. 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)

7. 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