The source of oxygen that drives the internal combustion engine in an automobile is air. air is a mixture of gases, which are principally n2 (~79%) and o2 (~20%). in the cylinder of an automobile engine, nitrogen can react with oxygen to produce nitric oxide gas, no. as no is emitted from the tailpipe of the car, it can react with more oxygen to produce nitrogen dioxide gas. write balanced chemical equations for both reactions. express your answers as chemical equations separated by a comma. identify all of the phases in your answer.