Lesson #1 Potential Energy Diagrams
Aim: How can the process of a chemical reaction be illustrated?
I. Potential Energy Diagrams = relationship between activation energy and heat of reaction for a chemical reaction 1. Activated Complex = temporary composite of atoms or molecules that will eventually form the products of the rxn. = highest point on diagram is potential energy of this composite = energy needed to form this composite = activation energy 2. Activation Energy - minimum amount of energy needed to form the Activated Complex and start the chemical reaction 3. Catalyst = atom or molecule that speeds up a chemical reaction when added to the rxn. = lowers peak of Activated Complex b/c takes less energy to make = Heat of reaction and potential energy of products don’t change. 4. Heat of Reaction = The heat released or absorbed in a chemical reaction. It is the difference between the Potential Energy of the Products and the Potential Energy of the Reactants
Heat of Reaction = PE Products - PE Reactants
A. Exothermic Rxn = Reactants --> Products + Heat Energy 1. self-sustaining i.e. burning match 2. spontaneous
3. Heat of Reaction is negative
4. Usually a reaction in which bonds are formed. 5. Feel warm to the touch as heat is released into the system. [pic]
B. Endothermic Rxn = Heat Energy + Reactants --> Products 1. non-spontaneous
2. Heat of Reaction is positive
3. Usually a reaction in which bonds are broken. 4. Feel cold to the touch as heat is removed from the system and absorbed into compounds...
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