Autoprotolysis constant product

Water dissociates to form ions according to Equation (6.2). The ionic product of the concentrations is the autoprotolysis constant Kw, according to Equation (6.4). Taking logarithms of Equation (6.4) yields ... 

Blood plasma is that part of the blood remaining after removal of the haemoglobin cells that impart a characteristic blood-red colour. According to Table 6.4, most people s plasma has a pH in the range 7.3-7.5. So, what is the concentration of solvated protons in such plasma We met the autoprotolysis constant Kw in Equation (6.4). Although we discussed it in terms of super-pure water, curiously the relationship still applies to any aqueous system. The product of the concentrations of solvated protons and hydroxide ions is always 10 14 at 298 K. 

The product of the molar concentrations (or, more accurately, the activities) of the species produced as a result of autoprotolysis. The autoprotolysis constant for water is K, equal to [H30+][0H ], or 1.0 x IQ i at 25°C. It is a temperature-dependent constant, increasing with... 

Symbol for the product of the H+ concentration (or, H3O+ concentration) and the OH concentration of an aqueous solution the autoprotolysis constant. See Water, Temperature Effects of pK, of... 

The autoprotolysis constant (autoionization constant) of water, Kw = q(l l jO )q(OI1 ) ss [H30+][0H, is often called the ion product constant of water. The value of -logKw varies with temperature as in Table 3.2. In water, there exists the following relation between K l of an acid and Kb of its conjugate base ... 

The product of these two concentrations is known as the ionization constant of water, Kyf (or as the ionic product of water, or maybe sometimes as the autoprotolysis constant, Kap)... 

The equilibrium can be described with the autoprotolysis constant, i.e., the product of the activities of the species produced as a result of autoprotolysis. For solvents in which no other ionization processes are significant the term is synonymous with ionic product . 

Autoprotolysis constant — The ion-product calculated from the ion activities of the conjugate acidic and basic species of an -> amphiprotic solvent (SH). The chemical equation of such self-ionization reactions can be schematized as 2HS H2S+ + S , where H2S+ is the conjugate cation, S the conjugate anion. The autoprotolysis constant can be formulated as JCauto = [H2S+] ... 

Ion product — A temperature-dependent constant related to pure substances that can dissociate forming ions and remain in equilibrium with them. It is the product of the ion activities raised to the stoichiometric coefficients of such ionic species in former pure substance. Since the concentration of the pure substance is practically a constant, it is not included in this equilibrium expression. Common pure substances characterized by an ion-product constant are -> amphiprotic solvents, and those salts that are partially dissolved in a given solvent. In the latter case, the ion product is synonymous with solubility product. The following table (Table 1) summarizes self-ionization ionic products and - autoprotolysis constants of some - amphiprotic solvents [i]. 

Ion product — Table. Autoprotolysis constants (Aauto = [SH J ] - [S ]) of some amphiprotic solvents SH . Values at 25 ° C unless stated otherwise... 

The autoprotolysis constant The extent of ionization (4-19) of a pure amphiprotic solvent is measured by the autoprotolysis constant SH> defined as the product Since the autoprotolysis reaction results in the formation of both solvent cations and solvent anions, the autoprotolysis constant is a measure of the differentiating ability of a solvent. If a solvent has a large Ash value, the existence in it of a wide range of strengths of either adds or bases is not possible. In contrast, if the autoprotolysis constant is small, adds and bases of varying strengths show titration curves distinctly different from each other. 

The extent of the autoprotolysis is a measure of both the acidic and basic strengths of the solvent and is given by the autoprotolysis constant or ionic product for example, for water K p = [H3O+] [OH ] = lO" (25°) and for sulfuric acid Kpp = [H3SOi+] [HSO4-] = 1.7 X 10- (10°). The autoprotolysis constant of sulfuric acid is greater than that for any other solvent that has been studied. Such a large value implies that, in spite of its very high acidity, sulfuric acid must also be appreciably basic. 

Values of the autoprotolysis constants and associated thermodynamic properties of the solvent are given in Appendix 3.3.3, and some selected values are in Table 3.3.4. Most of these are concentration products... 

The pJCj values are now available for many hydride complexes. Extensive tables have been compiled recently by Bullock and by Tilset. The rate of proton transfer to and from transition metals is rather slow (see below), so it is often possible to detect separate NMR signals for M-H and M , and tiius to determine the position of proton transfer equilibria between hydride complexes (M-H) and bases (B), or metal bases (M") and organic acids (HA). The pX values in Table 3.1 have been obtained in acetonitrile, an excellent solvent for acid-base chemistry because it solvates cations well enough to minimize ion pair formation it is both a weak acid and a weak base, with a very low autoprotolysis constant (ion product). ... 

The extent of this equilibrium can be characterized by the ionic product or the autoprotolysis constant Aap (eq. 8). The degree of autoprotolysis of solvents is... 

EAN IL was used in various reactions such as Biginelli reaction, condensation reaction, nitration of phenol, synthesis of P-amino ketone, ete. Nitration of phenol using ferric nitrate and clayfen in the IL, EAN, has been reported imder irltrasound irradiation [102]. Jaeger and Tucker in 1989 reported the Diels-Alder reaction involving EAN IL [ 103], IL EAN was prepared as per the literature method. EAN was found to be a more suitable solvent and catalyst for these reactions. In the presence of EAN, the reactions proceed in a shorter time, under milder conditions, and with excellent yield of products. EAN is liqttid at room temperature and is miscible with water thus, the separation and isolation of the product becomes easier. Its autoprotolysis constant is high, and the large electroactivity area and conductivity allow it to be used as a potential solvent. Araos et al. [104] reported the stability of a variety of lyotropic liquid crystals formed by a nttmber of polyoxyethylene nonionic surfactants in the room-temperature IL EAN. 

Values of the autoprotolysis constant (ionic product) for various amphiprotic solvents Kap/mol 1 at 25°C (except as otherwise indicated)... 

Now we come to a very important point that will be the basis of much of the discussion in this chapter and the next. Because Kw is an equilibrium constant. the product of the concentrations ofHjO+ and OH ions is always equal to Kw. We can increase the concentration of H30+ ions by adding acid, and the concentration of OH ions will immediately respond by decreasing to preserve the value of Kk. Alternatively, we can increase the concentration of OH ions by adding base, and the concentration of H30 ions will decrease correspondingly. The autoprotolysis equilibrium links the concentrations of H30+ and OH" ions rather like a seesaw when one goes up, the other must go down (Fig. 10.10). 

The activities (or, approximately, concentrations) of the solvo-acid and solvo-base (solvent minus a proton) are linked through the autoprotolysis or ion-product constant ... 

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