Nitrous Acid - Decomposition

Decomposition

In anything other than very dilute, cold solutions, nitrous acid rapidly decomposes into nitrogen dioxide, nitric oxide, and water:

2 HNO₂ → NO₂ + NO + H₂O

Nitrogen dioxide disproportionates into nitric acid and nitrous acid in aqueous solution:

2 NO₂ + H₂O → HNO₃ + HNO₂

In warm or concentrated solutions, the overall reaction amounts to production of nitric acid, water, and nitric oxide:

3 HNO₂ → HNO₃ + 2 NO + H₂O