k 1 k 1 Ag 2 Ce 3 fast Tl Ag 2 k2 Tl 2 Ag slowTl 2 Ce4 k 3 Tl3 Ce 3 fast The Ag

K 1 k 1 ag 2 ce 3 fast tl ag 2 k2 tl 2 ag slowtl 2

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+ k –1 k 1 Ag 2 + + Ce 3 + (fast) Tl + + Ag 2 + k 2 Tl 2 + + Ag + (slow) Tl 2 + + Ce 4 + k 3 Tl 3 + + Ce 3 + (fast) The Ag + ions are not permanently transformed since they are consumed in step 1 but regenerated in step 2.
Kinetics of Catalysis A heterogeneous catatyst is one present in a distinct phase, for example a solid surface in a gas-phase or solution-phase reaction. Extensively studied reaction: Platinum catalyst C 2 H 4 ( g ) + H 2 ( g ) C 2 H 6 ( g )
Kinetics of Catalysis Another heterogeneous catalyst: catalytic converter in your car, to reduce emission of unburned hydrocarbons, CO, and nitrogen oxides. CO, C x H y , O 2 catalyst CO 2 , H 2 O NO, NO 2 catalyst N 2 , O 2 Catalyst usually Pt or Rh on Al 2 O 3 support (large surface area). poisoned by heavy metals, for example Pb.
Kinetics of Catalysis Catalyst speeds up a reaction by increasing Arrhenius factor A , or more commonly lowering activation energy E a by providing a new activated complex of lower potential energy. Both forward and reverse reactions sped up by catalyst. Catalyst has no effect on thermodynamics. Inhibitor slows a reaction, often by increasing E a . Useful to prevent undesirable reactions.
Enzyme Catalysis

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