HNO2, also known as nitrous acid, is not classified as a strong acid. Instead, it is considered a weak acid.
In chemistry, strong acids are those that completely dissociate in water, meaning they release all of their hydrogen ions (H+) into the solution. Examples of strong acids include hydrochloric acid (HCl) and sulfuric acid (H2SO4).
On the other hand, weak acids only partially dissociate in water. This means that only a fraction of the acid molecules release their hydrogen ions. HNO2 falls into this category. When nitrous acid is dissolved in water, it only partially dissociates into hydrogen ions (H+) and nitrite ions (NO2–).
The partial dissociation of HNO2 can be represented by the following equilibrium equation:
HNO2 ⇌ H+ + NO2–
Because of this partial dissociation, nitrous acid is considered a weak acid. It is important to note that weak acids still play significant roles in various chemical reactions and processes, despite not being as strong as their counterparts.