You are asked to identify the activation energy for a reaction, to determine whether the reaction is endothermic or exothermic, and to calculate ∆E for the reaction.
You are given an energy diagram for a reaction.
The activation energy, E_{a}, is the difference in energy between the activated complex and the reactants. This value in the diagram is given as 113 kJ.
The energy of the products is lower than the energy of the reactants, which means that energy is released into the surroundings when the reaction takes place and the reaction is exothermic.
∆E is the difference in energy between the products and the reactants. The magnitude of this difference is 41 kJ. Because the energy of the products is lower than the energy of the reactants, ∆E = E_{products} − E_{reactants} = −41 kJ. Note that this exothermic reaction has a negative ∆E.