1. Factors Effecting Reaction Rate

2. Activation Energy
A certain amount of energy must be available to “propel” the molecules from one chemical state to another
This energy barrier is called the Activation Energy (Ea)‏
Arrangement of atoms that has this maximum energy is called the activated complex

3. Energy Profile

4. Collision Theory
In order to react molecules and atoms must touch each other.
They must hit each other hard enough to react.
Anything that increase these things will make the reaction faster.

5. Energy
Reactants
Products
Reaction coordinate

6. Activation Energy - Minimum energy to make the reaction happen
Reactants
Products
Reaction coordinate

7. Activated Complex or Transition State
Energy
Reactants
Products
Reaction coordinate

8. Energy
Reactants
Overall energy change
Products
Reaction coordinate

9. Things that Effect Rate
Temperature
- Higher temperature faster particles.
- More and harder collisions.
- Faster Reactions.
Concentration
- More concentrated closer together the molecules.
- Collide more often.
- Faster reaction.

10. Things that Effect Rate
Particle size
- Molecules can only collide at the surface.
- Smaller particles bigger surface area per volume.
- Smaller particles faster reaction.

11. Orientation Colliding alone is not enough to guarantee reaction
Relative orientations of the molecules may determine if the energy gets to the right place or if they are suitably oriented to form the new bonds
As temp increases, the number of collisions increases as does the fraction that are oriented correctly

12. Things that Effect Rate
Catalysts- substances that speed up a reaction without being used up.(enzyme).
- Speeds up reaction by giving the reaction a new path.
- The new path has a lower activation energy.
- More molecules have this energy.
- The reaction goes faster.
Inhibitor- a substance that blocks a catalyst.

13. Energy
Reactants
Products
Reaction coordinate

14. Homogenous Catalyst
Catalyst present in the same phase as the components of the reaction
Example: NO acts as a catalyst for the decomposition of ozone
NO provides another mechanism for the reaction which has a lower Ea

15. Heterogeneous Catalyst
Exists in a phase different from reactants
Catalyzed reactions of gases often occur at the surface of metals
Places where reacting molecules are absorbed on the metal surface are called active sites

16. Catalysts Hydrogen bonds to surface of metal. Break H-H bonds
Pt surface

17. Catalysts H H C C H H H H H H
Pt surface

18. Catalysts C C The double bond breaks and bonds to the catalyst.
Pt surface

19. Catalysts C C The hydrogen atoms bond with the carbon Pt surface H H H

20. Catalysts H H C C H H H H H H
Pt surface

21. Example A reaction occurs in a two step mechanism as shown
A + C → B + D (slow)
B + A → C + F (fast)
What substance acts as a catalyst?
What substance is an intermediate?
Write the overall reaction equation.
Write the rate law for the overall reaction.