Final answer:
HNO2 acts as an acid by donating a proton to water, resulting in the formation of NO2- and H3O+ ions, which is represented by the equation: HNO2(aq) + H2O(l) ⇌ NO2-(aq) + H3O+(aq).
Step-by-step explanation:
The chemical reaction depicting how HNO2 acts as an acid in aqueous solution can be illustrated by the reaction where the acid donates a hydrogen ion to water, forming the nitrite ion (NO2-) and the hydronium ion (H3O+). This is represented by the equation:
HNO2(aq) + H2O(l) ⇌ NO2-(aq) + H3O+(aq)
In this reaction, nitrous acid (HNO2) displays its acidic behavior by donating a proton (H+) to water (H2O), which then becomes hydronium ion (H3O+), while the remaining part of the molecule, the nitrite ion (NO2-), is what is left of the nitrous acid after losing the proton. This is an equilibrium process, typical for weak acids like nitrous acid in aqueous solutions. Nitrous acid is known to be unstable and only exists in solution, where it can act as an oxidizing agent or be subject to disproportionation into nitric acid (HNO3) and nitric oxide (NO) at varying conditions.