+k–1k1Ag2++Ce3+(fast)Tl++Ag2+k2→Tl2++Ag+(slow)Tl2++Ce4+k3→Tl3++Ce3+(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 catatystis one present in a distinct phase, for example a solid surface in a gas-phase or solution-phase reaction. Extensively studied reaction: Platinum catalyst C2H4(g)+H2(g)→C2H6(g)
Kinetics of Catalysis Another heterogeneous catalyst: catalytic converter in your car, to reduce emission of unburned hydrocarbons, CO, and nitrogen oxides. CO, CxHy, O2catalyst→CO2, H2ONO, NO2catalyst→N2, O2Catalyst usually Pt or Rh on Al2O3support (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 Eaby providing a new activated complex of lower potential energy. Both forward and reverse reactions sped up by catalyst. Catalyst has noeffect on thermodynamics. Inhibitor slowsa reaction, often by increasing Ea. Useful to prevent undesirable reactions.