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Energy Diagrams I

Energy Diagrams I. Dr. Rusay Fall 2004. A Reaction Coordinate Diagram. Gibbs standard free energy change ( D G o ). Enthalphy ( D H o ): the heat given off or absorbed during a reaction. Entropy ( D S o ): a measure of freedom of motion. Thermodynamic Quantities.

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Energy Diagrams I

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  1. Energy Diagrams I Dr. Rusay Fall 2004

  2. A Reaction Coordinate Diagram

  3. Gibbs standard free energy change (DGo) Enthalphy (DHo): the heat given off or absorbed during a reaction Entropy (DSo): a measure of freedom of motion Thermodynamic Quantities DGo = DHo - TDSo DG,DH,DS,DE are state functions E = q + w H = qp If DSo is small compared to DHo, DGo ~ DHo

  4. Example: PhotosynthesisEnergy Capture (Endergonic Reaction) n CO2(g) + n H2O(g) + energy 

  5. PhotosynthesisEnergy Capture (Endergonic Reaction) n CO2(g) + n H2O(g) + energy 

  6. PhotosynthesisEnergy Capture (Endergonic Reaction) n CO2(g) + n H2O(g) + energy  (CH2O) n (aq) + n O2(g) An Endothermic (Endergonic) Reaction

  7. Burning Gasoline (Octane) Exothermic Reactions : Energy Release 2 C8H18 + 25 O2 16 CO2 + 18 H2O

  8. Burning Gasoline (Octane) Exothermic Reactions : Energy Release 2 C8H18 + 25 O2 16 CO2 + 18 H2O

  9. Burning Gasoline (Octane) Exothermic Reactions : Energy Release 2 C8H18 + 25 O2 16 CO2 + 18 H2O An Exothermic (Exergonic) Reaction

  10. Burning Gasoline (Octane) Exothermic Reactions : Energy Release 2 C8H18 + 25 O2 16 CO2 + 18 H2O  H 16 CO2 + 18 H2O (Products are all the same.) Are isomers the same thermodynamically?

  11. Burning Gasoline (Octane) Exothermic Reactions : Energy Release 2 C8H18 + 25 O2 16 CO2 + 18 H2O A B C  H D 16 CO2 + 18 H2O (Products are all the same.) Which isomers are more stable thermodynamically? D > C > B > A

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