Final answer:
The mixture of concentrated nitric acid and concentrated sulfuric acid with benzene yields nitrobenzene, via a process called nitration, where benzene is substituted by a nitro group. The role of sulfuric acid is catalytic and also as an oxidizing agent in different contexts.
Step-by-step explanation:
When concentrated nitric acid is mixed with concentrated sulfuric acid and reacts with benzene at moderate temperature, the product formed is nitrobenzene. This reaction is known as the nitration of benzene, where a hydrogen atom (-H) on the benzene ring is substituted by a nitro group (-NO2). The sulfuric acid acts as a catalyst and helps in the generation of the nitronium ion (NO2+), which is the actual nitrating agent.
Hot, concentrated sulfuric acid is also an oxidizing agent, capable of oxidizing many compounds and undergoing reduction to various products depending on the conditions of the reaction. When diluted nitric acid is used, the output includes nitrogen monoxide (NO), whereas concentrated nitric acid produces nitrogen dioxide (NO2) instead.