Nitrous acid is a weak acid with the chemical formula HNO2. It is typically found in solution and is known for its role in various chemical reactions, particularly in the formation of nitrites. Nitrous acid is unstable and can decompose into nitrogen oxides and water, making it less commonly encountered in pure form. In the laboratory, nitrous acid is often generated by reacting sodium nitrite with a strong acid. It is important in organic chemistry for synthesizing certain compounds and can also play a role in biological processes, such as the conversion of amino acids into nitrosamines, which are of interest in toxicology.