Potential Energy Diagrams
These diagrams show how the potential energy in a chemical system changes as the reaction proceeds.
We can deduce many key pieces of information from a potential energy diagram:
- Enthalpy change; exothermic or endothermic
- Activation energy (Ea)
- Transition state complex/activated complex
- Presence of intermediates
See the image below (taken from Expii).
We are given that the enthalpy change, or ΔH is equal to -75 kJ/mol, and the activation energy. Because this is negative, we know that this is an exothermic reaction. Notice where the ΔH and activation energy take place on the exothermic potential energy diagram below.
The activation energy of the reverse endothermic reaction is equal to the sum of the absolute value of ΔH and the activation energy of the exothermic reaction.
Therefore, the activation energy of the reverse reaction would be 75 + (given Ea) kJ/mol.
