Equilibrium, for acid-base

The Bronsted-Lowry expression for acid-base equilibria (see Section 2.4)... 

In this way Kolthoff and Bruckenstein59 determined spectrophotometrically at 25° C for acid-base equilibria in glacial acetic acid the following ionization and dissociation constants of the bases ... 

Acid-base equilibria Partly Near-surface studies tend to investigate fresh or moderately saline water, which creates quite different conditions for acid-base equilibria. Studies of ocean geochemistry come closest to approximating deep-well conditions. 

Table 3.2 Equilibrium constants for acid-base equilibria at 25 °C, / = 0...

For acid-base equilibria in acetic acid, the original reports by Kolthoff and Bruckenstein are important [13]. Ref. [4] provides a comprehensive review of acid-base equilibria in amphiprotic solvents. 

The idea that the hydrogen ion can best be represented by the formula H30+ is widely accepted, and the characteristic form of the equations for acid-base equilibria in H20-D20 mixtures is a direct consequence of this assumption (Gold, 1960). In spite of the success of the simple theory in thus accounting for experimental results (see Section V) the assumption of the formula HsO+ was fairly recently called in question... 

The simplest example of the application of graphical representation of equilibrium data is that for acid-base equilibria involving a monoprotic acid, such as the acid HA, for which the equilibrium expression for solution in water may be written in terms of a concentration acidity constant, that is, an acidity constant valid at the appropriate temperature and corrected for activity by, f3r example, the Guntelberg approximation ... 

The paH (which can also be termed the pa or the pfi) is a practical unit consistent both with the experimental methods for pH measurements and with the thermodynamic equations for acid-base equilibria in the solvents concerned, but it should be noted that paH is a succession of scales rather than a single, universal scale of acidity. Consequently, two solutions in different solvent media may have the same paH but behave in totally different ways in acid-base reactions. 

If A° can be found and A is known for various stoichiometric concentrations, then values of a can be found at the various concentrations, and from these the equilibrium constant for dissociation into ions for the specihc electrolyte can be found. This provides an alternative route to Ks for acid/base equilibria. 

For acid-base equilibria the proton exchange reaction between HaO and H2O at standard conditions is assigned a free energy change of zero and an equilibrium constant of unity. It provides the datum to which all other acid base reactions are referenced. For redox equilibria, the... 

Furthermore, metal oxide electrode surfaces are sites for acid/base equilibria. This situation leads to a strong solution pH dependence of the surface charges and, therefore, the potential drop in the double layer. In the absence of specific ion adsorption other than H" and OH", there will exist a particular solution pH for which the excess surface charge on the metal oxide is zero. This value of pH is called the zero point of charge (not to be confused with the pzc). If specific adsorption of ions other than H" and OH" occurs, then the solution pH at which no excess surface charge exists is called the isoelectronic point or the point of zero zeta potential. ... 

Ionisation and Dissociation Constants for Acid-Base Equilibria in Anhydrous Acetic Acid at... 

An important application for acid-base equilibria is the analytic method called titration. With the help of titration, it is possible to investigate the composition of an initial solution using the equivalence point. Moreover, it can also be used to... 

The acidity of the phenol can influence the synthesis of phenolic resins. This parameter can be calculated for substituted phenolic compounds with the Hammett-equation [23], Surprisingly, it was found in the 1960 s that equation 8 can be applied to calculate the pK,-values for acid/base equilibria of disubstituted phenols [49] ... 

In the section on simulation, we first outline some key elements of the methodology used to carry out the simulations and their analysis. We comment specifically on the models used for the solvent, an area in which there has been considerable controversy. We then describe some of the derived results relating to single ion solvation structure and free energy, and the character of local density augmentation in this context. The reflection of this in activation free energies for ionic reactions and for acid-base equilibria, in particular, is then discussed. 

Equations such as (135) contain only vibrational frequencies, which can be derived from spectroscopic observations for species of not too great complexity. It should thus be possible to predict the isotope effect on simple equilibria, and this has been done successfully for a number of reactions in the gas phase. The problem is more difficult for reactions in solution, and few such quantitative predictions can be made for acid-base equilibria, though existing experimental data can be rationalized to some extent. 

It would be of interest to have more information about isotope effects for acid-base equilibria in non-exchanging solvents, especially those of higher dielectric constant such as dimethylformamide (e=37) and dimethyl sulphoxide (s = 49), in which ion association could be neglected. There are, however, considerable difficulties in carrying out and interpreting such measurements. 

From their method of measurement and definition, pH values are consistent with the thermodynamic equations for acid-base equilibria in the solvent system to which they apply. 

The sulfide melt is therefore characterized by the oxygen ion activity or by the Na20 activity, which depends on the oxygen and sulfur dioxide partial pressures. Therefore, instead of Na20, the basic component of the melt can also be characterized by the 0 ions. This allows the use of chemical nomenclature for acid-base equilibria, and can be described by the 0 ions which play a role analogous to the hydroxide ion in aqueous solutions... 

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