Upon contact, H 2O and HCl combine to form hydronium cations H 3O + and chloride anions Cl − through a reversible chemical reaction: In part because of its high polarity, HCl is very soluble in water (and in other polar solvents).
Consequently, the molecule has a large dipole moment with a negative partial charge (δ−) at the chlorine atom and a positive partial charge (δ+) at the hydrogen atom. The chlorine atom is much more electronegative than the hydrogen atom, which makes this bond polar. Hydrogen chloride is a diatomic molecule, consisting of a hydrogen atom H and a chlorine atom Cl connected by a polar covalent bond. Hydrochloric acid fumes turning pH paper red showing that the fumes are acidic
