# Explain with a well-labelled diagram, the concept of activation energy, and how a catalyst affects such energy?

The decisive factor is ${E}_{a}$, the energy of activation..... A catalyst can do NOTHING with respect to the enthalpy or free energy change of the reaction (i.e. the difference in energy between $X , Y$ and $Z$ in the diagram). A catalyst CAN alter ${E}_{a}$ by providing an alternative reaction pathway.
If the catalyst LOWERS ${E}_{a}$, then more of the reactant molecules have the requisite activation energy, and equilibrium should be reached more rapidly.