Ion concentration dependence

Acetoin consumes 4 equivalents of V(V) to produce some biacetyl via C-H fission however, this cleavage is not accompanied by a hydronium-ion concentration dependence of the rate thereby differing from a secondary alcohol oxidation. The mechanism of breakdown of the complex is depicted as follows... 

Figure 16(a) (O) shows the EMF responses of a 1,2-dichloroethane membrane containing anionic sites (KT/ C1PB). A Nernstian response was obtained. An SHG response to KCl was observed at activities of the latter above 10 M [Fig. 16(b), O]-These results can be interpreted in the same way as for ionophore-incorporated PVC liquid membranes, for which we have shown that the concentration of oriented cation complexes at the liquid-liquid interface can explain both the observed SHG signal and EMF response. The present SHG responses thus suggest primary ion concentration dependent charge separation at the interface of the 1,2-dichloroethane membranes incorporated with ionic sites. 

Fluorescence-based methods do not directly measure ionic current but, rather, measure either membrane-potential-dependent or ion-concentration-dependent changes of fluorescence signals (from fluorescent dyes loaded into the cytosol or cell membrane) as a result of ionic flux. Because fluorescence-based methods give robust and homogeneous cell population measurement, these assays are relatively easy to set up and achieve high throughput. 

The right terms in the two last equations, namely (dpB/dcB z ) and (31n ttBz /31ncBz ), are both called the thermodynamic or -> Wagner factors [iii, iv]. The first of them can be determined experimentally from the ion concentration dependence on the chemical potential of neutral species (a-T-S diagram). The direct determination of the second factor is impossible as the chemical potentials of charged species cannot be explicitly separated from those of other components of a system this parameter can be assessed indirectly, analyzing activities of all components. 

Figure 17 Average shell weights for whole G. sacculifer shells of glacial age as a function water depth. The open circles are for cores from the Ontong-Java Plateau, and the closed circles are for cores from the equatorial Atlantic. The vertical dashed line is the initial G. sacculifer weight obtained from measurements on Holocene samples from the Ceara Rise. The solid vertical line is the estimated initial weight for glacial-age G. sacculifer based on the assumption that the carbonate ion concentration dependence of initial shell weight established by Barker and Elderfield (2002)...

Speciation diagrams resulting from metal-ligand titrations, with the concentration profiles of the various MLn species throughout the process of successive addition of the ligand identified. At left is the pH-dependent formation of vanadyl complexes with the acetylacetonate anion at right is the chloride ion concentration-dependent formation of chloromercury(II) species. 

The oxidation of aminopolycarboxylic acids by Ce(IV) produces numerous species which can be used to infer mechanistic pathways. A more well-defined aspect of these systems is revealed in the initial steps of this class of reactions. Prior to the oxidation steps, Ce(IV) forms complexes with these compounds as demonstrated in the studies of Trubacheva and Pechurova (1981) and Hanna and Moehlenkamp (1983). The experimental constraints in the former study with ethylenediaminedisuccinic acid as the substrate resulted in a metastable complex formulated as Ce(OH)(EDDS) with log X,lab = 16.46. The subsequent redox reaction is extremely slow and exhibits a complex hydrogen ion concentration dependence. The latter system, wherein the substrate is A -benzyliminodiacetic acid (BIDA), was described in terms of the sequential reaction ... 

For aqueous electrolytes the ionic association become important when b is higher than 5, a value typical of a 2 2 electrolyte at room temperature or a 1 1 electrolyte above 300 °C. Thus, the extrapolation of the apparent partial volume of these electrolytes at infinite dilution to obtain the standard partial molar volume is uncertain, because the free ions concentration depends on the stoichiometric electrolyte concentration. For a 2 2 electrolyte, as MgS04, at 25 °C the apparent partial molar volume approach the DHLL value at concentrations bellow 0.01 mol kg (Franks and Smith, 1967) and, at least the density could be measured with a precision of 1 ppm, V° for MgS04 can not be obtained by extrapolation. In this case one can calculate the standard partial molar volume from the known values of standard partial volume of 1 2 and 1 1 electrolytes by using the additivity rule (Lo Surdo et al, 1982) ... 

The forward anodic process has no ion concentration dependence, but the backward cathodic process is proportional to the cathode H+ concentration. For both tIa and qc to be zero when / = 0, the kinetic expression for current density is... 

Parametrization of the thermodynamic properties of pure electrolytes has been obtained [18] with use of density-dependent average diameter and dielectric parameter. Both are ways of including effects originating from the solvent, which do not exist in the primitive model. Obviously, they are not equivalent and they can be extracted from basic statistical mechanics arguments it has been shown [19] that, for a given repulsive potential, the equivalent hard core diameters are functions of the density and temperature Adelman has formally shown [20] (Friedman extended his work subsequently [21]) that deviations from pairwise additivity in the potential of average force between ions result in a dielectric parameter that is ion concentration dependent. Lastly, there is experimental evidence [22] for being a function of concentration. There are two important thermodynamic quantities that are commonly used to assess departures from ideality of solutions the osmotic coefficient and activity coefficients. The first coefficient refers to the thermodynamic properties of the solvent while the second one refers to the solute, provided that the reference state is the infinitely dilute solution. These quantities are classic and the reader is referred to other books for their definition [1, 4],... 

It is apparent that there are differences in the behaviour of the BZ oscillators catalyzed by metal ions and metal-ion complexes, as is shown in Fig. 1 in case of temporal oscillations. Important features to be noted are (1) The frequency of oscillations decreases with increasing redox potential. (2) The amplitude of oscillations increases with increasing redox potential. (3) There is a characteristic change in the shape of an oscillatory cycle, which means that one of the most characteristic properties of the reaction, the critical Br -ion concentration, depends on the type of the catalyst. Also the heat evolution and the amount of bromomalonic acid produced during one oscillatory cycle were measured to be different for each of the four catalysts [7]. 

The dissolution and precipitation of limestone (CaCOs) underlie a variety of natural phenomena, such as the formation of limestone caverns. Whether a solution containing Ca and COs ions undergoes precipitation depends on the concentrations of these ions. In turn, the CC>3 ion concentration depends on the pH of the solution. To develop a better understanding of the conditions imder which CaCOs dissolves or precipitates, we must consider equilibrium relationships between Ca and COs , and between COs , HaO, and HCOs . This requirement suggests a need to combine ideas about acid-base equilibria from Chapters 16 and 17 with ideas about the new types of equilibria to be introduced in this chapter. 

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