Nitration of benzene is an electrophilic aromatic substitution reaction in which a nitro group -NO2 is introduced onto the benzene ring. The mechanism for the nitration of benzene involves the following steps:1. Formation of the electrophile: Nitric acid HNO3 reacts with a strong acid, usually sulfuric acid H2SO4 , to form the nitronium ion NO2+ , which acts as the electrophile in this reaction. HNO3 + H2SO4 NO2+ + HSO4- + H2O2. Electrophilic attack: The electrophile, NO2+, attacks the benzene ring, which is rich in electron density due to the presence of delocalized electrons. This attack results in the formation of a resonance-stabilized carbocation called the sigma complex or arenium ion.3. Deprotonation: A base, usually the bisulfate ion HSO4- , abstracts a proton from the sigma complex, restoring the aromaticity of the benzene ring and forming the nitrobenzene product. Sigma complex + HSO4- Nitrobenzene + H2SO4The effect of varying the concentration of nitric acid on the rate of reaction can be understood in terms of the rate law for the reaction. The rate law for electrophilic aromatic substitution reactions is generally of the form:Rate = k [Electrophile] [Benzene]In the case of nitration of benzene, the electrophile is the nitronium ion NO2+ , which is formed from nitric acid. Therefore, increasing the concentration of nitric acid will lead to an increase in the concentration of the nitronium ion, which in turn will increase the rate of the reaction. Conversely, decreasing the concentration of nitric acid will decrease the rate of the reaction.It is important to note that the reaction conditions, such as temperature and the presence of other catalysts, can also influence the rate of the reaction. Additionally, the use of excess nitric acid can lead to the formation of dinitrobenzene or other poly-nitro products, which may be undesirable depending on the specific application.