Which statement best explains the role of a
catalyst in a chemical reaction?
(1) a catalyst is added as an additional reactant
and is consumed but not regenerated.
(2) a catalyst limits the amount of reactants used.
(3) a catalyst changes the kinds of products produced.
(4) a catalyst provides an alternate reaction pathway
that requires less activation energy.

The answer is (4). If you look at a Maxwell-Boltzmann energy curve, you will see that lowering the activation energy will increase the proportion of molecules with sufficient energy for a successful reaction collision. Therefore, a reaction with lower activation energy will proceed more quickly. Often, this lower activation energy is obtained by another mechanistic pathway. Catalysts increase reaction speed through these two basic mechanisms.

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