Module 8.5: Catalysis

I catalysts: substances that provide an alternative pathway for a chemical reaction

1. often the alternative pathway tends to lower the activation energy of the reaction

2. this increases the overall rate of reaction, but does not change the equilibria

   1. both the forward and reverse rate are increased

3. A mechanism may involve a catalyst but cannot be present in neither the reactant or product side of the final chemical equation

   1. the catalyst must remain unchanged in the process

II homogeneous catalysts: catalysts in the same phase as the reaction mixture

1. enzymes, catalysts that regulate biological processes, are common homogeneous catalysts

III heterogeneous catalysts: catalysts that is in a different phase than to the reaction mixture

1. catalysts that utilize adsorption are very common

   1. often involves gas molecules (adsorbate) adsorbing to the metal surface (adsorbent), forming either a chemical bond (chemisorption)

   2. adsorption may also occur through van der Waals interactions (physisorption)

2. as the surface area of the adsorbent increases, so does the reaction rate