The sulfurous acid is inorganic and weak acid that could be taken as the aqueous solution of sulfur dioxide in water. The chemical formula for the substance is written as H2SO3 with a molecular weight 82.07 g/mol.
The chemical structure of the molecule is also given below where on sulfur atom is connected with one oxygen atom by double bond and two hydroxyl groups by single bonds only.
The natural occurrence of the compound can be felt in the acid rain when sulfur dioxide reacts together with atmospheric moisture. It is usually prepared by mixing SO2 and water together and the reaction can be reversed quickly to decompose the reactants again.
SO2 + H2O → H2SO3
This is the reason why the sulfurous molecule is not usually available in the acid form bur frequently used as sodium or potassium salts. This is a colorless molecule with a strong pungent smell and quite unpleasant too. The density of the molecule is 1.03 g/mL approx. and a boiling point of minus 60 degree Celsius. This is unstable and hard to find in the pure isolated state. It’s a weak acid and reacts with bases to form sulfites and potassium salts.
If we look at the uses closely then it is used as a disinfectant and wonderful reducing agent too. This acid cannot be availed as a free agent and its health effects are not so severe like other similar acids. However, when exposed to air, it could become toxic and corrosive too.