During the 1970 s, at the time when catalytic converters...

During the $1970 \mathrm{~s}$, at the time when catalytic converters began to be installed on automobiles, tetraethyllead, which had been added to gasoline to improve the octane rating, was gradually phased out. In the combustion chamber of the engine the four ethyl groups in tetraethyllead are converted to carbon dioxide and water, leaving either elemental lead or lead(II) oxide. In a modern automobile, burning a single tank of leaded gasoline can ruin the catalytic converter, destroying nearly all of the catalytic activity. Based on what you learned about the mechanism of reactions in a catalytic converter, suggest a reason that lead in gasoline might destroy the catalyst's ability to speed up reactions.

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Key Concepts

Catalyst Poisoning

Catalyst poisoning occurs when a substance, such as lead compounds, binds strongly or irreversibly to the active sites on a catalyst's surface. This binding prevents the reactants from accessing these sites, thereby significantly reducing or completely inhibiting the catalytic activity. In the context of catalytic converters, the deposition of lead byproducts on the noble metal catalysts blocks these active sites, disrupting the intended oxidation and reduction reactions necessary for emission control.

Catalysis

Catalysis refers to the process by which a catalyst speeds up a chemical reaction by lowering the activation energy needed for the reaction to proceed. This is typically achieved by providing an alternative pathway for the reaction, and in many cases, especially in heterogeneous catalysts like those used in catalytic converters, the reaction takes place on the surface of the catalyst where reactants are adsorbed, reacted, and then desorbed as products.

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