kinetics lesson 7 catalysts. 1. catalysts participate in reaction 1.a+b→c 2.c+d→cd...
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KineticsLesson 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: C CD
2- Catalysts Reduce Ea
2- Catalysts Reduce Ea
PE(kJ)500
400
300
200
100
0reaction path
H forward =H reverse =Ea forward uncat =Ea reverse uncat =Ea forward cat =
PE(kJ)500
400
300
200
100
0reaction path
H forward = -300 kJH reverse =Ea forward uncat =Ea reverse uncat =Ea forward catalyzed =
PE(kJ)500
400
300
200
100
0reaction path
H forward = -300 kJH reverse = +300 kJEa forward uncat =Ea reverse uncat =Ea forward catalyzed =
PE(kJ)500
400
300
200
100
0reaction path
H forward = -300 kJH reverse = +300 kJEa forward uncat = 100 kJEa reverse uncat =Ea forward catalyzed =
PE(kJ)500
400
300
200
100
0reaction path
H forward = -300 kJH reverse = +300 kJEa forward uncat = 100 kJEa reverse uncat = 400 kJEa forward catalyzed =
PE(kJ)500
400
300
200
100
0reaction path
H forward = -300 kJH reverse = +300 kJEa forward uncat = 100 kJEa reverse uncat = 400 kJEa 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)500
400
300
200
100
0reaction 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)
Catalysts change mechanism of reaction (Introduce more steps)
Uncatalyzed reactionCatalyzed reaction
Catalysts change mechanism of reaction (Introduce more steps)
Downhill in PEKE 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:
Summary1. 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 H2SO4 Many Organic Reactions
Pt Surface Catalyst for Diatomic Gases Pd Catalytic Converter Automobile
Convert CO → CO2
Rh Catalytic Converter Automobile
Convert NO2 → N2 + O2
Biological Catalysts Enzymes Biological Catalysts
Amylase
pepsin
Commercial Catalysts H2SO4 Many Organic Reactions
Pt Surface Catalyst for Diatomic Gases Pd Catalytic Converter Automobile
Convert CO → CO2
Rh Catalytic Converter Automobile
Convert NO2 → N2 + O2
Biological Catalysts Enzymes Biological Catalysts
Amylase
pepsin
Pt surface
HH
HH
HH
HH
• Hydrogen bonds to surface of metal.
• Break H-H bonds
Surface Catalysts
Pt surface
HH
HH
Catalysts
C HH C
HH
Pt surface
HH
HH
Catalysts
C HH C
HH
• The double bond breaks and bonds to the catalyst.
Pt surface
HH
HH
Catalysts
C HH C
HH
• The hydrogen atoms bond with the carbon
Pt surface
H
Catalysts
C HH C
HH
H HH
The Metal-Catalyzed Hydrogenation of Ethylene
Exothermic Reaction
Downhill in PEKE is produced
H
Ea(rev)(cat)Ea(for)(cat)
Ea(for)(uncat) Ea(rev)(uncat)
Workbook Page 36
Question 62- 63