Topic: Kinetics

1. Topic: Kinetics

2. Video

3. 2 things needed for a reaction to occur • X amount of activation energy • Effective collisions Particle Diagram of Collision NO + O3 NO2 + O2 Activated Complex is NOT in equation!

4. Kinetics tells how fast a reaction will occur • Reaction rate = speed of the reaction • Depends on Frequency of collisions (how often they occur) and efficiency of collisions • Rate = Concentration of reactant or product time Appearance of products Disappearance of reactants

5. Collision Theory • Molecules must collide in order to react • Effective collisions lead to formation of products • Effective Collisions = • Energetic • Favorable orientation • Ineffective collisions do not lead to products

6. Most collisions are NOT effective!

7. Why Do Collisions Have to be Energetic? • KE of reactants is used to overcome reaction barrier • KE is transformed into PE

8. Factors that determine reaction rates • Nature of reactants (ions vs molecules)

9. Nature of the reactants:Ions or Molecules? • Ions in solution react quickly • Covalently bonded molecules react slowly • takes time to break all those bonds! • 2 gas phase reactants react more quickly than 2 liquids or 2 solids

10. Factors that determine reaction rates • Nature of reactants (ions vs molecules) • Temperature

11. Increase in Temperature • Temp = measure of average KE of molecules in system • faster molecules are moving, will collide more often • faster molecules are moving, more energetic the collisions

12. Factors that determine reaction rates • Nature of reactants (ions vs molecules) • Temperature • Concentration

13. Concentration • Increase in concentration: • more particles per unit volume – more collisions in given amount time

14. Factors that determine reaction rates • Nature of reactants (ions vs molecules) • Temperature • Concentration • Pressure (gases only)

15. Pressure • systems involving gases changing pressure analogous to changing concentration •  Pressure,  # particles per unit volume • Increase reaction rate • ↓ Pressure, ↓ # particles per unit volume • Decrease reaction rate

16. Factors that determine reaction rates • Nature of reactants (ions vs molecules) • Temperature • Concentration • Pressure (gases only) • Surface Area

17. Surface Area • Higher surface area • more particles exposed for reaction • Higher surface area means smaller particle size • (For heterogeneous reactions)

18. Homogeneous Reaction: • all reactants in same phase • Heterogeneous Reaction: • reactants in different phases

19. Factors that determine reaction rates • Nature of reactants (ions vs molecules) • Temperature • Concentration • Pressure (gases only) • Surface Area • Presence of a catalyst

20. Catalyst • Substance that increases rate of reaction without itself being consumed • does not participate in reaction • Lowers the activation energy for the reaction

21. Catalyst/enzyme written above the arrow