Final answer:
The formula of nitrous acid is HNO₂, which is a weak and unstable acid only present in aqueous solutions and can disproportion into other nitrogen compounds upon heating.
Step-by-step explanation:
The formula of nitrous acid is HNO₂. Nitrous acid is a weak and unstable acid that exists only in aqueous solution and can be prepared by adding an acid to a solution of nitrite. In chemical reactions, the nitrite ion (NO₂⁻) combines with hydronium ions (H₃O⁺) to form nitrous acid:
NO₂ (aq) + H₃O⁺ (aq) → HNO₂ (aq) + H₂O(l)
Nitrous acid is known to disproportionate into nitric acid (HNO₃) and nitric oxide (NO) when heated. Additionally, it acts as an oxidizing agent with reducing agents, while it can be oxidized to nitric acid by strong oxidizing agents.