Potential Energy Diagrams
Energy
Does a Reaction Diagram simply go from one
Energy level to another?
C + O2
The system has
given away 395
kJ to the
surroundings
395kJ
C O2
Exothermic Reaction
Reactants
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GHS Honors Chem
How do we visualize the energy
needed to break the O2 bond?
Energy
C+2O
• Shows the reaction pathway, or the change in
energy during a chemical reaction … here’s an
Endothermic example:
The
Activated
Complex
is the
unstable
intermedi
ate
395kJ
Exothermic Reaction
Reactants
→
Products
The Potential Energy Diagram
C + O2
The system has
given away 395
kJ to the
surroundings
→
CO2
Products
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The Potential Energy Diagram
• Conversely, an Exothermic Reaction
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In an Exothermic Reaction …
• reaction that
releases
energy
• products have
lower PE
than reactants
energy
released
2H2(l) + O2(l) → 2H2O(g) + energy
GHS Honors Chem
GHS Honors Chem
1
In an Endothermic Reaction …
• reaction that
absorbs
energy
• reactants have
lower PE
than products
What if We Add a Catalyst?
• A Catalyst lowers the Energy of the Activation
Complex
energy
absorbed
• The Activation Energy (EA) is lowered for both
directions
2Al2O3 + energy → 4Al + 3O2
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GHS Honors Chem
Potential Energy
Diagram Worksheet
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2