How do you read a potential energy diagram?

Potential energy diagrams are used to measure the potential energy shifts throughout a reaction and as tracking the trends, they can also help you better grasp the steps present in a reaction.

are used to measure the potential energy shifts throughout a reaction. As well as tracking the trends, they can also help you better grasp the steps present in a reaction.

This picture is a basic PE diagram, like on you would see on a regents, or other tests.

A: This is the potential energy for the reactants, from 0 to where the line stops. (Stage 1)

B: This is the energy required for the reaction to take place, its from the energy in the reactants to the curve, or activation energy. (aka Stage 2)

C: This is in general of the whole graph, is it sometimes placed to either the left or the right. Its the potential energy of the activated complex, or the total energy involved.

D: This is the energy present in the products. (Stage 3)

Things You Can Tell From This:

The heat of reaction (delta T), this is the difference from the PE of the reactants (A) and the PE of the products (D). Delta T = PE of products - PE of reactants.

Exo Or Endo? You would tell this by whether the products have more or less energy than the reactants. If the products have more (positive heat of reactants), the products line will be higher than the reactants, making it an endothermic reaction, because energy is absorbed. BUT, if the products PE is lower (like this one), the reaction is exo, because you lost heat.

CATALYSTS: These are molecules that lower the activation energy, by providing an alternate path for the reaction to take place. This actually lowers the activation energy, shrinking both the energy of activation (B) and the activated complex (B)