Oxoacids strengths

Many of the inorganic oxoacids are strong (i.e. have negative PX3 values) in aqueous solution. But, as we have seen, use of a solvent with a lower proton affinity than water (for example pure ethanoic (acetic) acid makes it possible to differentiate between the strengths of these acids and measure pX values. The order of strength of some typical oxoacids is then found to be (for H X -> H , X- + H") ... 

Regularities in the observed strengths of oxoacids have been formulated in terms of two rules by L. Pauling and others ... 

Trends in acid strength can be explained in terms of molecular structure. In an oxoacid molecule, the hydrogen atom that dissociates is bonded to oxygen, which in turn is bonded to a nonmetal atom, X. The ionization in water of an oxoacid H—O—X can be represented as... 

Relate oxoacids to the corresponding oxides and compare their acid strengths. 

Oxidation A half-reaction in which there is an increase in oxidation number, 88 chromium, 548 electrolysis and, 498 fluorine, 557 halogens, 557-558 oxoacids, 568-570 oxoanions, 568-570 species strength, 506-507q transition metals, 546t zinc, 86-87... 

Oxoacid (continued) acid strength of, 567-568 oxidizing strength, 568-570 reducing strength of, 568-570 Oxoacids, 42... 

The acid strengths and oxidizing abilities of the halogen oxoacids increase with the oxidation number of the halogen. The hypohalous acids, HXO (halogen oxidation number +1), are prepared by direct reaction of the halogen with water. For example, chlorine gas disproportionates in water to produce hypochlorous acid and hydrochloric acid ... 

The interhalogens have properties intermediate between those of the constituent halogens. Nonmetals form covalent halides metals tend to form ionic halides. The oxoacids of chlorine are all oxidizing agents both acidity and oxidizing strength of oxoacids increase as the oxidation number of the halogen increases. 

The strength of an oxoacid increases as more and more electron density is withdrawn from the O—H bond. 

Although the oxoacids of selenium and sulfur have comparable acid strengths (pITai 2.6 vs. p fa 1-9, respectively, for the quadrivalent species pA a 3 for both the hexavalent species), the hydride H2Se is much more acidic than H2S (pATai 3.9 vs. 7.0). Thus, while thiols such as cysteine are mainly protonated at physiological pH, selenols such as selenocysteine are predominantly dissociated under the same conditions. 

The relative strength of oxoacids increases with the number of oxygen atoms. 

Discuss the factors that can be used to predict the relative strength of different oxoacids. 

The Dependence of Acid Strengths of Oxoacids on the Oxidation State of the Central Element... 

Two comparisons are discussed in this section (a) the acid strengths of the oxoacids of the second period, H3B03, H2C03 and HN03, and (b) those of the oxoacids of the third period, H3P04, H2S04 and HC104. 

The acid strengths and oxidizing abilities of the halogen oxoacids (Table 15.8) increase with the oxidation number of the halogen. The... 

Because dissociation of an oxoacid requires breaking an O — H bond, any factor that weakens the O — H bond or increases its polarity increases the strength of the acid. Two such factors are the electronegativity of Y and the oxidation number of Y in the general reaction... 

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