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Potential Energy Diagrams: Understanding Energy Changes in Chemical Reactions, Study notes of Physics

An overview of potential energy diagrams, their role in illustrating energy changes during chemical reactions, and key concepts such as reactants, products, and transition states. Topics covered include endothermic and exothermic reactions, activation energy, and catalysts.

Typology: Study notes

2021/2022

Uploaded on 09/12/2022

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8.9 Potential Energy Diagrams Notes
A. Potential Energy Diagram (also called: Reaction Coordinate)
1. Potential energy diagrams show changes in ___________
energy of substances over a course of a reaction.
2. Reactants _________________________ Products
a) ___________________: substances that are
present at the beginning of the reaction
b) ___________________: substances that are
present at the end of the reaction
c) _____________________________ (transition
state): a high energy intermediate substance that is
formed during the reaction.
1. Very ____________
2. Usually not shown in the _________ (like above)
Activation energy: Reactants to Activated Complex (Hill)
H = Products - Reactants
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8.9 Potential Energy Diagrams Notes A. Potential Energy Diagram (also called: Reaction Coordinate)

  1. Potential energy diagrams show changes in ___________ energy of substances over a course of a reaction.
  2. Reactants  _________________________  Products a) ___________________: substances that are present at the beginning of the reaction b) ___________________: substances that are present at the end of the reaction c) _____________________________ (transition state): a high energy intermediate substance that is formed during the reaction. 1. Very ____________ 2. Usually not shown in the _________ (like above)

Activation energy: Reactants to Activated Complex (Hill) ∆H = Products - Reactants

B. Endothermic Vs Exothermic reactions

  1. Exothermic reactions release energy (______) so the potential energy __________________ in order to become products
  2. Endothermic reactions absorb energy (______) so the potential energy __________________ in order to become products

C. Example questions

  1. Is the forward reaction endothermic or exothermic?
  2. Which letter represents the potential energy of the reactants in the forward direction?
  3. Which letter represents the potential energy of the products in the reverse direction? 4. Which letter represents the potential energy of the activated complex? 5. Which letter represents the activation energy in the forward direction? 6. Draw in a line to represent the heat of the reaction (H). 7. What is the difference between the (H) in the forward and reverse directions? - What is the activation energy for the reverse reaction? - What is the activation energy for the forward reaction?

D. Catalyst Catalysts speed up reactions by lowering the activation energy. How do the features on the diagram change with the addition of a catalyst?

  • Reactants? - Activation energy (forward)?
  • Products? - P.E. of the activated complex?
  • H? - Activation energy (reverse)?