Catalysis

• What type of catalysis part-takes in the reaction but is chemically unchanged afterwards?

  homogeneous
• what are the two types of catalysts?

  Positive

  negative
• what is a positive catalyst?

  accelerates reaction
• what is a negative catalyst?


  slows down reaction
• Does a catalyst participate in the reaction?


  yes
• is the active form the same as in the form not involved in the reaction?

  no may be very different
• which type of catalysis more commonly changes physical form before/after reaction?

  heterogeneous
• Do catalyst show in rate laws?


  yes
• do catalysts show up in stoichiometric equation?

  no
• Do catalysts effect position of equilibrium?

  No
• what is a heterogeneous reaction mechanism?

  adsorption -> surface diffusion -> reaction -> desorption
• what is the importance of heterogeneous catalysts with crystalline structure?

  deangling bonds
• what are some issues with heterogeneous catalysts?

  catalyst poisoning and expensive
• what are issues with homogeneous catalysis?

  enzyme (denatured), hard to separated afterward
• what type of catalyst is used industrally?

  heterogeneous
• what kind of plot do hetergeneous catalysis produce?

  volcano plot
• what is the action of a catalyst?

  Lowers activation energy, thus increasing rate constant k and the reaction rate
• Do a catalyst lower gibbs free energy?

  No
• what are the two types of adsorption?


  Physical, chemical
• describe physisorption:

  • weak interactions (van der waals)
  • easily reversed
  • non-specific
  • low heat of adsorption (mildly exothermic)
  • No activation E barrier
  • multi-layer adsorption possible
• Describe chemisorption:

  • Strong interactions (partial covalent)
  • less readily reversed (due to better binding strength)
  • specific
  • maybe higher enthalpy of adsorption
  • small activation E barrier
  • monolayer adsorption is the norm