is important in the manufacturing of sulfuric acid. Chlorine oxides Chlorine(I) oxide reacts with water to form hypochlorous acid, a very weak acid: Cl2O + H2O <=> 2 HOCl Chlorine(VII) oxide reacts with water to form perchloric acid, a strong acid: Cl2O7 + H2O → 2 HClO4 Iron oxides Iron(II) oxide is the anhydride of the aqueous ferrous ion: [Fe(H2O)6]^2+ -> FeO + 2H+ + 5H2O Chromium oxides Chromium trioxide is the anhydride of chromic acid: H2CrO4 -> H2O + CrO3 Vanadium oxides Vanadium trioxide is the anhydride of vanadous acid: 2H3VO3 -> 3H2O + V2O3 Vanadium pentoxide is the anhydride of vanadic acid: 2H3VO4 -> 3H2O + V2O5 See also Organic acid anhydride, similar compounds in organic chemistry Base anhydride References