Dual Enrollment Environmental Science Practice Exam

A catalytic converter is an emissions control device placed in the exhaust stream of an internal combustion engine. It uses catalysts—usually platinum, palladium, and rhodium—to speed up chemical reactions that transform the harmful exhaust gases into less harmful ones. In the typical three-way catalytic converter, carbon monoxide and unburned hydrocarbons are oxidized to carbon dioxide and water, while nitrogen oxides are reduced to nitrogen and oxygen. This reduces emissions of CO, hydrocarbons, and NOx, producing CO2, H2O, and N2 as the main byproducts. It works best at the high temperatures found in exhaust and when the engine runs near the ideal air-fuel ratio; fuels with lead or other poisons can disable the catalyst. This device is different SAMPLEfrom components that merely cool exhaust or alter engine timing and does not add fuel to the system.