A catalyst increases the rate of a rxn without being consumed.

  They provide an alternate mechanism.

  Lower activation energy.

  Ex: O3(g) + O(g) 2 O2(g)

  Decomposition of O3 catalyzed with Cl from CFCs.

  Cl + O3 ClO + O2

  ClO + O Cl + O2

  Homogeneous catalysts exist in the same phase as reactants.

  Heterogeneous catalysts exist in a different phase than reactants.

  Gas or liquid reactants adsorb, or stick to a solid surface.

  Catalytic converter – pollutants in car exhaust stick to Pt/Pd surface to break down.

  Hydrogenation – alkenes (C=C) convert to alkanes (C-C) on Pt surface.

  Four Steps: 1.  Adsorption of reactants. 2.  Diffusion (migration) until

reactants approach each other. 3.  Reaction to form products. 4.  Desorption of products.

  Enzymes – biological protein catalysts.

  Both homogeneous and heterogeneous properties.

  Reactants called substrates and bond to active site.

 Read section 12.8

 Ch. 12: #65-70 all