• # question_answer Nitric acid acts only as an oxidising agent while nitrous acid acts both as an oxidising as well as a reducing agent. Why?

(i)$HN{{O}_{3}}$: Oxidation number of N is $HN{{O}_{3}}=+5$ Maximum oxidation number of N = + 5 Minimum oxidation number of N = -3 Since the oxidation number of N in $HN{{O}_{3}}$is maximum (+5), therefore, it can only decrease by accepting electrons. Hence, $HN{{O}_{3}}$ acts only as an oxidising agent. (ii)$HN{{O}_{2}}$: Oxidation number of N in $HN{{O}_{2}}=+3$ Maximum oxidation number of N = + 5 Minimum oxidation number of N = - 3 Thus, the oxidation number of N can either increase by losing electrons or can decrease its O.N by accepting electrons. Therefore, $HN{{O}_{2}}$ acts both as an oxidising as well as a reducing agent.