Kinetics and Equilibrium Mrs. Paparella December 7, 2006

Exothermic Potential Energy Diagram

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

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

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.

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?

Endothermic Potential Energy Diagram

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