The basicity of Sulphurous acid is two.
What is basicity?
The number of hydronium ions (H3O+) that can be formed by ionising one molecule of an acid in aqueous solution is known as the acid’s basicity.
H2SO3 is a chemical compound with chemical name Sulphurous acid. The other names of sulphurous acid are Sulfur dioxide solution or dihydrogen trioxosulfate or trioxosulfuric acid. Trioxosulfuric acid is a colourless liquid with a strong burning sulphur odour. It is corrosive to tissue and metals. It is a sulfur oxoacid, tautomer of a sulfonic acid, and conjugate acid of a hydrogensulfite.