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Kinetics Lesson 5 PE Diagrams Mechanisms

Kinetics Lesson 5 PE Diagrams Mechanisms. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products.

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Kinetics Lesson 5 PE Diagrams Mechanisms

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  1. Kinetics Lesson 5 PE Diagrams Mechanisms

  2. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products

  3. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products

  4. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products

  5. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products

  6. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products Potential Energy

  7. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products Potential Energy

  8. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products max Potential Energyhigh  low

  9. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products max Potential Energyhigh  low Kinetic Energy

  10. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products max Potential Energyhigh  low Kinetic Energy high min low

  11. Potential and Kinetic Energy Changes during a Collision Endothermic Reactants Activated Complex Products max Potential Energyhigh  low Uphill- endothermic! Kinetic Energy high min low

  12. Pick the slow and fast reaction

  13. Ea Ea Pick the slow and fast reaction

  14. Ea Ea Pick the slow and fast reaction Slow Fast- low Ea

  15. Reaction Mechanisms Consider the following reaction: 4 HBr(g) + O2(g) → 2H2O(g) + 2Br2(g) Watch Simulation- set both temperature and mass to the highest setting. Set red to 1 and blue to four and remove the barrier. How often do all five particles collide? There are five reactant particles. If there are three or morereactant particles they will not likely react in one step. They will react in a series of steps, which is a mechanism.

  16. Mechanism 1. HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast PE Reaction Path

  17. Mechanism 1Cancel out identical formulas to get the overall equation. HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast PE Reaction Path

  18. Mechanism 1Cancel out identical formulas to get the overall equation. HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast PE Reaction Path

  19. Mechanism 1Intermediates are produced and then consumed and cross out from right (first) and left (second). HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast PE Reaction Path

  20. Mechanism 1What is left is the overall reaction. HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast PE Reaction Path

  21. Mechanism 1What is left is the overall reaction. HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast 4HBr(g) + O2(g) → 2H2O(g)+ 2Br2(g) PE Reaction Path

  22. Mechanism 1Step 1, which is the slow step, is called the rate determining step and has the highest activation energy. HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast 4HBr(g) + O2(g) → 2H2O(g)+ 2Br2(g) PE Reaction Path

  23. Mechanism 1 HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast 4HBr(g) + O2(g) → 2H2O(g)+ 2Br2(g) A potential energy diagram for this reaction might look like this. PE Reaction Path

  24. Mechanism 1 HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast 4HBr(g) + O2(g) → 2H2O(g)+ 2Br2(g) A potential energy diagram for this reaction might look like this. PE Reaction Path

  25. Mechanism 1 HBr(g) + O2(g) → HOOBr(g)slow HBr(g) + HOOBr(g) → 2HOBr(g) fast 2HOBr(g) +2HBr(g) → 2H2O(g)+ 2Br2(g) fast 4HBr(g) + O2(g) → 2H2O(g)+ 2Br2(g) highest A potential energy diagram for this Mechanism has three humps The slow step has the highest Ea Ea(rev) Ea PE Reaction Path

  26. The Rate Determining Step The slowest step in the reaction mechanism is called the rate-determiningstep. It has the highest Ea. To increase the rate, you must increase the rate of this step. Increasing the rate of a fast step will not increase the rate of the overall reaction.

  27. Identifying a Catalyst in a Mechanism A catalyst is not consumed in the reaction. It is used in one step; it speeds up the reaction, and then is regenerated in a later step. A catalyst will cancel out but will be on the left side in an earlier step than on the right side.

  28. Identifying a Catalyst in a Mechanism A catalyst is not consumed in the reaction. It is used in one step; it speeds up the reaction, and then is regenerated in a later step. A catalyst will cancel out but will be on the left side in an earlier step than on the right side. C → → C

  29. Identifying a Catalyst in a Mechanism A catalyst is not consumed in the reaction. It is used in one step; it speeds up the reaction, and then is regenerated in a later step. A catalyst will cancel out but will be on the left side in an earlier step than on the right side. C → → C

  30. Identifying a Catalyst in a Mechanism A catalyst is not consumed in the reaction. It is used in one step; it speeds up the reaction, and then is regenerated in a later step. A catalyst will cancel out but will be on the left side in an earlier step than on the right side. C → → C An intermediate is produced and then consumed. It will be on the right side in an earlier step than on the left side.

  31. Identifying a Catalyst in a Mechanism A catalyst is not consumed in the reaction. It is used in one step; it speeds up the reaction, and then is regenerated in a later step. A catalyst will cancel out but will be on the left side in an earlier step than on the right side. C → → C An intermediate is produced and then consumed. It will be on the right side in an earlier step than on the left side. → I I →

  32. Identifying a Catalyst in a Mechanism A catalyst is not consumed in the reaction. It is used in one step; it speeds up the reaction, and then is regenerated in a later step. A catalyst will cancel out but will be on the left side in an earlier step than on the right side. C → → C An intermediate is produced and then consumed. It will be on the right side in an earlier step than on the left side. → I I →

  33. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: Intermediate:  

  34. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: Intermediate:  

  35. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: Intermediate:   C

  36. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: Intermediate:   C

  37. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: Intermediate:   C CD

  38. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: Intermediate:   C CD

  39. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: Catalyst: D Intermediate:   C CD

  40. Mechanism 2 1. A + B → C 2. C + D → CD 3. CD + E → ABE + D Overall Equation: A + B + E → ABE Catalyst: D Intermediate:   C CD

  41. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Intermediates: PE Reaction Path

  42. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Intermediates: PE Reaction Path

  43. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: PE Reaction Path

  44. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl PE Reaction Path

  45. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl ΔH = Ea (forward) =   Ea (reverse) = The enthalpy of Br The enthalpy of BrCl 800 PE 600 400 200 Reaction Path

  46. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl ΔH = 200 kJ Ea (forward) = Ea (reverse) = The enthalpy of Br   The enthalpy of BrCl PE Reaction Path 800 600 400 200

  47. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl ΔH = 200 kJ Ea (forward) =   Ea (reverse) = The enthalpy of Br   The enthalpy of BrCl PE Reaction Path 800 600 400 200

  48. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl ΔH = 200 kJ Ea (forward) = 600 kJ Ea (reverse) = The enthalpy of Br   The enthalpy of BrCl PE Reaction Path 800 600 400 200

  49. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl ΔH = 200 kJ Ea (forward) = 600 kJ Ea (reverse) = 400 kJ The enthalpy of Br   The enthalpy of BrCl PE Reaction Path 800 600 400 200

  50. Mechanism 3 Step 1 Br2 → 2Br Step 2 Br + OCl2 → BrOCl + Cl Step 3 Br + Cl → BrCl Overall Reaction: Br2 + OCl2 → BrOCl + BrCl Intermediates: Br Cl ΔH = 200 kJ Ea (forward) = 600 kJ Ea (reverse) = 400 kJ The enthalpy of Br 300 kJ The enthalpy of BrCl PE Reaction Path 800 600 400 200

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