One of the components of polluted air is NO. It is formed in the high- temperature environment of internal combustion engines by the following reaction: $$\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}(g) \quad \Delta H=180 \mathrm{kJ}$$ Why are high temperatures needed to convert \(\mathrm{N}_{2}\) and \(\mathrm{O}_{2}\) to NO?

The given reaction is a synthesis reaction between nitrogen gas (\(\mathrm{N}_{2}\)) and oxygen gas (\(\mathrm{O}_{2}\)) to produce nitric oxide (NO). The reaction can be represented as: \[\mathrm{N}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}(g)\] The energy change for this reaction is provided: \(\Delta H=180 \mathrm{kJ}\), which means this is an endothermic reaction, as it requires an input of energy to take place.

Activation energy, according to the collision theory of chemical reactions, is the minimum energy required for reactant molecules to collide and form an activated complex, which then leads to the formation of products. In an endothermic reaction, it requires more energy for the activation energy to be reached, as compared to an exothermic reaction. In such a case, the higher the temperature, the more reactant molecules will possess the required activation energy for the reaction to occur.

High temperatures are needed to convert \(\mathrm{N}_{2}\) and \(\mathrm{O}_{2}\) to NO for the following reasons: 1. High temperatures provide the necessary energy for the reaction to proceed, since it is an endothermic reaction. Higher temperatures cause a rise in the average kinetic energy of the molecules, increasing the likelihood that they possess sufficient energy to overcome the activation energy barrier. 2. Both \(\mathrm{N}_{2}\) and \(\mathrm{O}_{2}\) molecules have strong triple and double bonds, respectively. These bonds require a large amount of energy to be broken, which can be supplied by high temperatures. 3. Higher temperatures lead to more frequent and energetic collisions between reactant molecules, increasing the probability of the formation of the activated complex that eventually forms NO. As a result, the reaction rate is faster at higher temperatures. In conclusion, high temperatures are needed to convert \(\mathrm{N}_{2}\) and \(\mathrm{O}_{2}\) to NO because the reaction is endothermic and requires a substantial amount of energy to break the strong bonds in the reactants and facilitate the formation of the activated complex, which eventually results in the formation of NO.