Chemistry – Chemical reactions - Rate of reaction | e-Consult

The presence of a catalyst (e.g., C) in the reaction A → B lowers the activation energy (E_a).

The energy profile of the reaction will be altered. The peak representing the activation energy will be shifted downwards.

This means that less energy is required for the reaction to proceed. As a result, a larger fraction of reactant molecules will have sufficient energy to overcome the activation energy barrier and form product B.

The overall enthalpy change (ΔH) of the reaction remains unchanged by the presence of the catalyst, as the catalyst only affects the rate at which the equilibrium is reached. The catalyst provides an alternative pathway with a lower E_a, but the difference in energy between reactants and products (ΔH) is unaffected.