Nitrous acid is obtained by the action of dilute HCl or H2SO4 on any nitrite. KNO2 + HCl → KCl + HNO2 NaNO2 + HCl → NaCl + HNO2 KNO2 + H2SO4 → KHSO4 + HNO2 Nitrous acid is obtained when di-nitrogen tri-Oxide is dissolved in cold water. N2O3 + H2O → 2HNO2 HNO2 is obtained by the action of barium nitrite and cold and dilute H2SO4.

oxyacid, any oxygen-containing acid. Most covalent nonmetallic oxides react with water to form acidic oxides; that is, they react with water to form oxyacids that yield hydronium ions (H3O+) in solution. There are some exceptions, such as carbon monoxide, CO, nitrous oxide, N2O, and nitric oxide, NO. The strength of an oxyacid is defined by the extent to which it dissociates in water (i.e.