1. Potential Energy Diagrams

2. For a given reaction, the Activation Energy and the Enthalpy of Reaction can be shown graphically in a Potential Energy Diagram by plotting PE against a reaction coordinate which represents the progress of the reaction. Reaction Coordinate Potential Energy→ Enthalpy of Reaction Activation Energy

3. Potential Energy Diagrams A catalyst is a substance that changes the speed of reactions by changing the activation energy. Catalysts that speed up reactions do so by ___________ the activation energy and changing the reaction pathway. Catalysts have no effect on a reaction’s heat of reaction. Reaction Coordinate Potential Energy→ Activation Energy with no catalyst Enthalpy of Reaction Activation Energy with a catalyst lowering

4. 1 a) Endothermic Reactions: N 2(g) + O 2(g) → 2 NO (g)  H R = + 182.6 kJ The activated complex is a temporary arrangement of atoms. A - ________________________ B - ________________________ C - ________________________ 1 - ________________________ 2 - ________________________ 3 - ________________________ 4 - ________________________ 5 - ________________________ 6 - ________________________ 7 - ________________________ Reaction Coordinate Potential Energy→ A C B 5 7 4 3 2 6 reactants activated complex products PE of reactants activation energy catalyzed reaction pathway PE of activated complex heat of reaction reverse activation energy PE of products Potential Energy Diagrams

5. N 2(g) + O 2(g) → 2 NO (g)  H R = + 182.6 kJ Ex.1) The “energy barrier” for the forward reaction is represented by arrow _____. Ex.2) The net amount of energy absorbed is represented by arrow _____ Ex.3) When 4 moles of NO (g) are produced, the energy absorbed by the reactants is __________ kJ + 365.2 2 5

6. Potential Energy Diagrams Ex.4) If a catalyst were introduced into the reaction, which arrow(s) would NOT change? __________ Ex.5) A catalyst speeds up a reaction because it changes the reaction mechanism for the reaction and thus _____________ the activation energy. Ex.6) Do the products above have a greater, lesser, or equal amount of stored energy as the reactants? Explain. __________________________________ _________________________________________ 1, 5, & 7 lowers The products have a greater amount of stored energy than the reactants because the reaction is endothermic.

7. Potential Energy Diagrams Ex.7) Rewrite the reaction equation above putting the heat into the equation. __________________________________________ Ex.8) What is an activated complex? __________________________________________ An activated complex is an unstable temporary N 2(g) + O 2(g) + 182.6 kJ → 2 NO (g) arrangement of atoms formed after the reactants have begun to react.

8. b) Exothermic Reactions: CO (g) + NO 2(g) → CO 2(g) + NO (g) + 226 kJ The activated complex is a temporary arrangement of atoms. 1 X - ________________________ Y - ________________________ Z - ________________________ 1 - ________________________ 2 - ________________________ 3 - ________________________ 4 - ________________________ 5 - ________________________ 6 - ________________________ 7 - ________________________ Reaction Coordinate Potential Energy→ X Z Y 5 7 4 3 2 6 reactants activated complex products PE of reactants activation energy catalyzed reaction pathway PE of activated complex heat of reaction reverse activation energy PE of products Potential Energy Diagrams

9. CO (g) + NO 2(g) → CO 2(g) + NO (g) + 226 kJ Ex.1) The energy liberated when 0.5 mole of NO 2(g) is consumed is __________ kJ. Ex.2) The energy difference between the reactants and the products is represented by arrow _____. Ex.3) The energy of the activated complex is represented by arrow _____. 113 7 6

10. Potential Energy Diagrams Ex.4) A catalyst speeds up a reaction because it changes the _____________________swag__ for the reaction and thus lowers the activation energy. Ex.5) Rewrite the reaction equation above putting the heat off to the side of the equation. __________________________________________ Ex.6) What letter or number represents the temporary unstable grouping of atoms? _____ Ex.7) Rewrite the reaction equation above putting the heat off to the side of the equation. _________________connorwashere_____________ ____________ reaction mechanism Y CO (g) + NO 2(g) → CO 2(g) + NO (g) ΔH = -226 kJ A + B → ABΔH = +50 kJ

11. Potential Energy Diagrams Ex.8) Given the reaction: A + B + 50 kJ → AB If the activation energy is 55 kJ, then the reverse activation energy would be _______ kJ. Reaction Coordinate Potential Energy → 55 kJ 50 kJ ? kJ 5

12. Potential Energy Diagrams Ex.9) During an endothermic reaction, (1) the enthalpy is decreased (2) there is no activation energy (3) the enthalpy is increased (4) the reaction is slow Ex.10)The net quantity of energy absorbed by an endothermic reaction (1) is greater than the activation energy (2) is less than the activation energy (3) is equal to the activation energy (4) can not be compared to the activation energy