ENTHALPY

1. ENTHALPY Activation energy, the activated complex, and the effect of a catalyst

2. Learning Objectives • The activated complex is an unstable arrangement of atoms formed at the maximum of the potential energy barrier, during a reaction. • The activation energy is the energy required by colliding molecules to form an activated complex. • The activation energy can be calculated from potential energy diagrams. • The effect of a catalyst can be explained in terms of alternative reaction pathways with lower activation energy. • A potential energy diagram can be used to show the effect of a catalyst on activation energy.

3. ACTIVATION ENERGY

4. Energy Reactants Products Reaction Progress

5. Energy EA Reactants DH Products Reaction Progress

6. Energy Reactants DH Products Reaction Progress

7. Energy Reactants DH Products Reaction Progress

8. Energy EA Reactants DH Products Reaction Progress

9. What happens here? Energy EA Reactants DH Products Reaction Progress

10. THE ACTIVATED COMPLEX

11. Reactant A

12. Reactant A Reactant B

16. Activated complex

17. Activated complex

18. Activated complex

20. Product C Product C

21. Activated Complex Energy EA Reactants A + B DH Product C Reaction Progress

22. THE EFFECT OF A CATALYST

23. NUMBER OF MOLECUES WITH A PARTICULARENERGY Ea MOLECULAR ENERGY

24. NUMBER OF MOLECUES WITH A PARTICULARENERGY EXTRA MOLECULES WITH SUFFICIENT ENERGY TO OVERCOME THE ENERGY BARRIER Ea MOLECULAR ENERGY

25. Effect of catalyst Without catalyst Energy EA Reactants DH Products Reaction Progress

26. Effect of catalyst Energy With catalyst Reactants DH Products Reaction Progress

27. Effect of catalyst Energy EA With catalyst Reactants DH Products Reaction Progress

28. Effect of catalyst Without catalyst Energy EA Reactants DH Products Reaction Progress

29. Effect of catalyst Energy EA With catalyst Reactants DH Products Reaction Progress

30. Effect of catalyst Without catalyst Energy EA EA With catalyst Reactants DH Products Reaction Progress