Although both N2 and O2 are naturally present in the air we breathe, high levels of NO and NO2 in the atmosphere occur mainly in regions with large automobile or power plan emissions. The equilibrium constant for the reaction of N2 and O2 to give NO is very small. The reaction is, however, highly endothermic, with a heat of reaction equal to +180 kJ (Equation 5).

N2(g) + O2(g) + 180 kJ <> 2NO(g) Equation 5

Use LeChâtelier's Principle to explain why the concentration of NO at equilibrium increases when the reaction takes place at high temperatures.