1. Kinetics and Equilibrium
Mrs. Paparella
December 7, 2006

2. Exothermic Potential Energy Diagram

3. Exothermic Potential Energy Diagram
Activation
energy
Energy of
Activated
Complex
Delta H ( DH)
PE reactants
PE products

4. Exothermic Potential Energy Diagram
In an exothermic reaction, the products always have less energy than
the reactants because some heat is released to the environment.
The temp of the surroundings goes up.
Activation
energy
Energy of
Activated
Complex
Delta H ( DH)
PE reactants
PE products

5. The activation energy is the additional energy needed to get the reaction started.
The activated complex is a very unstable complex of all the atoms as they are breaking bonds and reforming into the products.
The Delta H is also called the Heat of the Reaction and is always found by:
DH = Products Energy – Reactants Energy.
The Delta H is negative for exothermic rxs
and positive for endothermic rxs.

6. Look at Table I Which reaction is the most exothermic?
Which reaction is the least exothermic?
What happens to the temperature of the water that is used to dissolve Sodium hydroxide?
What reaction is the most endothermic?
What reaction is the least endothermic?
What happens to the temperature of the water that is used to dissolve Sodium Chloride?
What is the unit for heat of reaction?

7. Endothermic Potential Energy Diagram

8. Endothermic Potential Energy Diagram
In an endothermic reaction the products have more energy than the reactants and the Delta H is always positive. The temp of the surroundings get colder b/c heat is absorbed from the surroundings.
Activation
energy
Energy of Activated Complex
Delta H ( DH) PE
products
PE reactants