• # question_answer 18) While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reactions, ozone and nitric acid act only as oxidants why?

Sulphur is of 5th group. Thus, maximum oxidation state of sulphur will be +6 and minimum oxidation state will be -2. In${{H}_{2}}S$, sulphur is in -2 state. Thus, ${{H}_{2}}S$ can undergo oxidation only and it acts as a reductant only. In$S{{O}_{2}}$, sulphur is in +4 state. Thus, $S{{O}_{2}}$ can undergo both oxidation as well as reduction, i.e., it may act both as oxidising and reducing agent. Ozone acts only as an oxidising agent because it decomposes to give nascent oxygen. ${{O}_{3}}\rightleftharpoons {{O}_{2}}+[O]$ In$HN{{O}_{3}}$, nitrogen has maximum oxidation state of+5; hence nitrogen can undergo only reduction, i.e., it can act only as oxidising agent.