Unit 4: Kinetics

1. Unit 4: Kinetics Activation Energy and Catalysts

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

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

5. Exothermic Reactions Exothermic: energy EXITS the system E<0 (neg.) System Energy Surroundings

6. Endothermic Reactions Endothermic: energy ENTERS the system E>0 (pos.) System Energy Surroundings

7. 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

8. 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)

9. 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 Once the reaction has occurred, the catalyst releases the molecule(s) and finds another one to help