Oxygen Acids of Sulfur, Selenium, and Tellurium

H2SO4 8H2O contains also H5O2 ions and H2O molecules according to the formulation (11502)2(804)-41120.  

Single crystals of peroxomonosulfuric acid, H2SO5 (also known as Caro s acid) have been prepared by the reaction of fuming sulfuric acid and H2O2. In the crystal structure, the molecules are conneeted via hydrogen bonds. The distance within the peroxo group of the anion is 1.46 A. 

H2S04 8H20 contains also H502+ ions and H20 molecules according to the formulation (H502)2(S04)-4H20.48 

In contrast to sulfurous acid, H2S03, which is not known as pure substance, the respective selenium compound can be obtained in crystalline form. H2Se03 crystallizes with the non-centrosymmetric space group P2 2,2] and contains pyramidal H2Se03 molecules.54 Within the molecules the bond lengths Se-O and SeOH differ by about 10 pm and the molecules are connected to puckered layers by strong hydrogen bonds. 

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