Spark-ignition engine exhaust gases contain several air pollutants including the oxides of nitrogen, NO and NO2, collectively known as NOx. Additionally, the exhaust gases may contain carbon monoxide (CO) and unburned or partially burned hydrocarbons (HC). The pollutant amounts actually present depend on engine design and operating conditions, and they typically differ significantly from values calculated on the basis of chemical equilibrium. Discuss both the reasons for these discrepancies and ssible mechanisms by which such pollutants are formed in an actual engine. In a memorandum, summarize your findings and conclusions.