Kinetics Lesson 7 Catalysts

1. Catalysts Participate in reaction 1.A+B→C 2.C+D→CD 3.CD+E→ABE+D Catalyst: Intermediate:

1.Catalysts Participate in reaction 1.A+B→C 2.C+D→CD 3.CD+E→ABE+D Overall Equation:A +B + E →ABE Catalyst:D Intermediate: CCD

2- Catalysts Reduce Ea

PE(kJ) reaction path  H forward=  H reverse= Ea forward uncat= Ea reverse uncat= Ea forward cat =

PE(kJ) reaction path  H forward=-300 kJ  H reverse= Ea forward uncat= Ea reverse uncat= Ea forward catalyzed =

PE(kJ) reaction path  H forward=-300 kJ  H reverse=+300 kJ Ea forward uncat= Ea reverse uncat= Ea forward catalyzed =

PE(kJ) reaction path  H forward=-300 kJ  H reverse=+300 kJ Ea forward uncat=100 kJ Ea reverse uncat= Ea forward catalyzed =

PE(kJ) reaction path  H forward=-300 kJ  H reverse=+300 kJ Ea forward uncat=100 kJ Ea reverse uncat=400 kJ Ea forward catalyzed =

PE(kJ) reaction path  H forward=-300 kJ  H reverse=+300 kJ Ea forward uncat=100 kJ Ea reverse uncat=400 kJ Ea forward catalyzed =50 kJ

PE(kJ) reaction path Slow rate due to high Ea

PE(kJ) reaction path The only way to change the PE diagram is to add a catalyst.

PE(kJ) reaction path The only way to change the PE diagram is to add a catalyst. Catalyst DO NOT change enthalpy change of a reaction

PE(kJ) reaction path Slow rate due to high Ea

PE(kJ) reaction path

3. Catalysts enable more molecules to jump over the hill

4.Catalysts change mechanism of reaction (Introduce more steps)

Catalysts change mechanism of reaction (Introduce more steps)

Uncatalyzed reaction Catalyzed reaction

Catalysts change mechanism of reaction (Introduce more steps) Downhill in PE KE is produced Ea(for)(uncat)

Catalysts change mechanism of reaction (Introduce more steps) Ea(for)(cat) Ea(for)(uncat)

4. Uncatalysed Reaction continues to occur even in the presence of Catalysts

5. Inhibitors slow down reaction rate by providing mechanism (route) of high Ea. So a small fraction of collision have sufficient energy to jump over the hill.

6. Reaction continues to take place even if catalyst is removed because reaction will produce catalyst. 1.A+B→C 2.C+D→CD 3.CD+E→ABE+D Catalyst:

Summary 1.Participate in the reaction 2.First used then made in the following step 3.Only factor that can lower Ea and change PE diagram, ΔH does not change. 4.Catalysts enable more molecules to jump over the hill 5.Change mechanism(introduce more steps) 6.Un-catalysed reaction continue to take place 7.Inhibitors slow down reaction by increasing Ea 8.Removal of all the catalyst does not stop the reaction

Commercial Catalysts Biological Catalysts

Commercial Catalysts H 2 SO 4 Many Organic Reactions PtSurface Catalyst for Diatomic Gases PdCatalytic Converter Automobile ConvertCO→CO 2 RhCatalytic Converter Automobile ConvertNO 2 →N 2 + O 2 Biological Catalysts EnzymesBiological Catalysts Amylase pepsin

Commercial Catalysts H 2 SO 4 Many Organic Reactions PtSurface Catalyst for Diatomic Gases PdCatalytic Converter Automobile ConvertCO→CO 2 RhCatalytic Converter Automobile ConvertNO 2 →N 2 + O 2 Biological Catalysts EnzymesBiological Catalysts Amylase pepsin

Pt surface HHHH HHHH Hydrogen bonds to surface of metal. Break H-H bonds Surface Catalysts

Pt surface HHHH Catalysts C HH C HH

Pt surface HHHH Catalysts C HH C HH The double bond breaks and bonds to the catalyst.

Pt surface HHHH Catalysts C HH C HH The hydrogen atoms bond with the carbon

Pt surface H Catalysts C HH C HH HHH

The Metal-Catalyzed Hydrogenation of Ethylene

Exothermic Reaction Downhill in PE KE is produced HH Ea(rev)(cat) Ea(for)(cat) Ea(for)(uncat) Ea(rev)(uncat)

Workbook Page 36 Question