Oxygen acids, strength

Hydrolysis of Salts. Anion hydrolysis cation hydrolysis hydrolysis in general. Buffered solutions. Coordination number of elements formulas of the oxygen acids. Strengths of the oxygen acids. Simple rules. General concepts of acids and bases. Proton donors and acceptors. Acid strength and tendency to undergo condensation. 

If the formulae of the acids are written as shown on the right, it becomes apparent that acid strength increases as the number oj oxygen atoms not involved in O—bonding increases. 

A 5—6% sodium hypochlorite solution is sold for household purposes, of which the largest use is in laundry. Solutions of 10—15% NaOCl are sold for swimming pool disinfection, institutional laundries, and industrial purposes. Solutions of various strengths are used in household and industrial and institutional (I I) cleaners, disinfectants, and mildewcides. A small amount is used in textile mills. Sodium hypochlorite is also made on site with 30—40 g/L available chlorine for pulp bleaching, but its use is decreasing in order to reduce chloroform emissions (see Chlorine oxygen acids and salts). 

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... 

Strategy The structure can be obtained by removing an oxygen atom from H O, (Figure 21.8). Relative acid strengths can be predicted on the basis of the electronegativity and oxidation number of the central nonmetal atom, following the rules cited above. 

Martra and coworkers studied low-temperature CO and room-temperature CO2 adsorphon on Na- and Ba-exchanged X and Y zeolites [138]. They were able to determine from the CO adsorphon IR data that Ba ions located in the Sn sites in both X and Y zeolites exhibit higher Lewis acid strength compared to Na ions in the same sites. Furthermore, the Lewis acid shength of both Ba and Na ions was dependent on the framework aluminum content of the zeolite. Using CO2 as a probe, they found that subshtuhng Na with Ba caused a reduchon in the basicity of the framework oxygens in proximity to the cahons. 

Since phenol has an appreciable dipole moment, and no low energy acceptor orbitals, it should interact best with the donors that have the largest lone pair dipole moment — the oxygen compounds. Iodine has no dipole moment and the interaction with iodine is expected to be essentially covalent. Iodine should interact best with the donors that have the lowest ionization potential, i.e., the ones whose charge clouds are most easily polarized. Similar considerations have been employed to explain the donor strengths of primary, secondary and tertiary amines 35a) and the acid strengths of (35b) ICl, Bt2, I2. CeHsOH and SO2. 

Although the ions NOs, P04, S04 and C104 are not completely ionic, there is still an appreciable charge difference between the central atom and the oxygen atoms. Since, in all probability, the bonds are semipolar, the positive charges on the central atom are one for NOacid strength can still be applied. 

Oxygen acids that do not contain a single central atom have strengths corresponding to reasonable extensions of the rules, as shown by the following examples ... 

The acid strengths in the sequence Si(OH)4, PO(OH)j, SOt(OH), ClOa(OH) can be discussed qualitatively in a simple way. The bonds from the central atoms have the strengths 1, , f, and , respectively, leaving each oxygen atom with further bonding power of 1, f, , and J, respectively, for hydrogen. In consequence, silicic acid is a very weak acid, phosphoric acid is a weak acid, sulfuric acid is a strong acid, and... 

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