Nitric acid acts only as an oxidising agent while nitrous acid acts both as an oxidising as well as reducing. Explain.

Explanation

(i) `HNO_3` Oxidation number of N in `NHO_3` is +5.
Maximum oxidation number of N is +5 because it has five electrons in the valence shell `(2s^(2)2p^3)` .
Minimum oxidation number of N is -3 because it can accept 3 more electrons to get noble gas configuration.
Since O.N. of N in `HNO_3` is maximum , therefore , it can only decrease . Thus , `HNO_3` can act as an oxidising agent.
(ii) `HNO_2` Oxidation number of N = +3
Maximum O.N. = +5
Minimum O.N. of N = -3
Therefore , the O.N. of N can increase by losing electrons or can decrease by accepting electrons. Thus, `HNO_2` can act both as an oxidising as oxidising as well as a reducing agent.