It reacts to form sulphurous acid H2SO3. Unlike Sulphuric acid H2SO4, sulphurous acid is a weak acid and only partially dissociates in solution
H2O + SO2 ⇌ H2SO3
H2SO3 + H2O ⇌ HSO3- + H3O+
Pure H2SO3 cannot however be isolated, as it decomposes back to sulphur dioxide gas & water if evaporation is attempted. The sulphite and bisulphite ions (conjugate bases) for the acid are however fairly common.