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?

Answer:

                (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.