Ionic interactions electrolytes

Finally, it must be recalled that the transport properties of any material are strongly dependent on the molecular or ionic interactions, and that the dynamics of each entity are narrowly correlated with the neighboring particles. This is the main reason why the theoretical treatment of these processes often shows similarities with models used for thermodynamic properties. The most classical example is the treatment of dilute electrolyte solutions by the Debye-Hiickel equation for thermodynamics and by the Debye-Onsager equation for conductivity. 

Conway, B. E., Ionic interactions and activity behaviour, CTE, 5, Chap. 2 (1982). Friedman, H. L., Ionic Solution Theory, Wiley-Interscience, New York, 1962. Harned, H. S., and B. B. Owen, The Physical Chemistry of Electrolytic Solutions, Reinhold, New York, 1950. 

Electrolytes are used to promote the exhaustion of direct or reactive dyes on cellulosic fibres they may also be similarly used with vat or sulphur dyes in their leuco forms. In the case of anionic dyes on wool or nylon, however, their role is different as they are used to facilitate levelling rather than exhaustion. In these cases, addition of electrolyte decreases dye uptake due to the competitive absorption of inorganic anions by the fibre and a decrease in ionic attraction between dye and fibre. In most discussions of the effect of electrolyte on dye sorption, attention is given only to the ionic aspects of interaction. In most cases, this does not create a problem and so most adsorption isotherms of water-soluble dyes are interpreted on the basis of Langmuir or Donnan ionic interactions only. There are, however, some observed cases of apparently anomalous behaviour of dyes with respect to electrolytes that cannot be explained by ionic interactions alone. 

The fact is, ionic interaction between dyes, fibres and electrolytes is only part of the story. As Yang [1] has pointed out, hydrophobic interactions also need to be taken into consideration. Whilst this has been accepted for many years in relation to dye-fibre interactions, the extension of the concept to interactions involving neutral electrolytes is novel. 

Polyelectrolytes are long chain molecules bearing ionisable sites. It is not always possible to predict with confidence the extent to which polyelectrolytes behaviour is exhibited. Thus, polyacrylic acid in water is only weakly ionised and in dioxan it behaves as a typical non-electrolyte. It is usual to overcome the complications imposed by ionic interactions by the inclusion of simple salts and LS studies in salt-free solutions are rather rare. The problems have been discussed recently by Kratochvil137), whilst the review of Nagasawa and Takahashi138 constitutes one of the few devoted exclusively to LS from polyelectrolyte solutions. LS from many biopolymers such as proteins is, of course, extremely relevant in this context. 

The pressure-volume-temperature (PVT) properties of aqueous electrolyte and mixed electrolyte solutions are frequently needed to make practical engineering calculations. For example precise PVT properties of natural waters like seawater are required to determine the vertical stability, the circulation, and the mixing of waters in the oceans. Besides the practical interest, the PVT properties of aqueous electrolyte solutions can also yield information on the structure of solutions and the ionic interactions that occur in solution. The derived partial molal volumes of electrolytes yield information on ion-water and ion-ion interactions (1,2 ). The effect of pressure on chemical equilibria can also be derived from partial molal volume data (3). 

The PVT properties of aqueous solutions can be determined by direct measurements or estimated using various models for the ionic interactions that occur in electrolyte solutions. In this paper a review will be made of the methods presently being used to determine the density and compressibility of electrolyte solutions. A brief review of high-pressure equations of state used to represent the experimental PVT properties will also be made. Simple additivity methods of estimating the density of mixed electrolyte solutions like seawater and geothermal brines will be presented. The predicted PVT properties for a number of mixed electrolyte solutions are found to be in good agreement with direct measurements. 

This equation contains the activity coefficients 71, 72, and 7. Recall from the Debye-Hiickel treatment of ionic interactions in dilute solutions that the magnitude of these coefficients shows the following dependence on ionic strength fi for a solution of electrolytes ... 

The value of the electrophoretic mobility can be calculated considering the migration of an ion in an electrolyte solution at inhnite dilution where no ionic interactions occur. Under the action of an electric held, the ion is accelerated by a force Pa, directed toward the appositively charged electrode, which is given by... 

Anionic polymerization Initiated by electron transfer (e.g., sodium-naphthalene and styrene In THF) usually produces two-ended living polymers. Such species belong to a class of compounds called bolaform electrolytes (27) In which two Ions or Ion pairs are linked together by a chain of atoms. Depending on chain length, counterion end solvent, Intramolecular Ionic Interactions can occur which in turn may affect the dissociation of the ion pairs Into free ions or the llgand-lon pair complex formation constants. 

For water at 25 °C, e (which is dimensionless) is 78.5, and for the very nonpolar solvent benzene, e is 4.6. Thus, ionic interactions are much stronger in less polar environments. The dependence on r2 is such that ionic attractions or repulsions operate only over short distances—in the range of 10 to 40 run (depending on the electrolyte concentration) when the solvent is water. 

Effective encounter distances for reaction of solvated electrons with electron scavengers at room temperature compared with crystallographic encounter distances Unless otherwise noted, the solvent is water (containing an inert electrolyte in some cases). Corrections for ionic interactions according to eqn. (106) were applied and reaction rate coefficient were extrapolated to zero ionic strength (Chap. 3, Sect. 1.6 and 1.7). Many of these studies have been mentioned in Chap. 3, Sect. 2... 

This equation is precisely equal to that in the Debye-Hiickel treatment of ionic interaction for dilute electrolyte solutions14, only that the distance x refers to a central ion (point charge) and not to an electrode. In the Debye-Hiickel case, since the central ion is small and 0A small we can make the approximation (elinear approximation is not valid. 

The first accurate calculation of the activity coefficient based on energetic effects of inter-ionic interactions in solvents was carried out by -> Debye and -> Huckel in 1923 by assuming that all the deviations from ideality at low concentrations of electrolyte were due to interionic interactions (- Debye-Huckel theory) with this it is possible to show that... 

The physics of electrostatics in aqueous solution has attracted scientists notice for centuries. At present, the solvation of ions, volumes and radii of ions in solution, and ionic interactions are still hotly debated research fields. Recently, thermodynamic, transport and structural data were mutually employed for gaining fruitful physicochemical insights into electrolyte solutions [2]. This chapter recapitulates the essential... 

The distinction between drinking water and seawater is obvious. Electrolyte solutions, as the name suggests, involve neutral components that separate into electrically non-neutral units, ions. Ionic interactions are q q y r for a pair of ions with formal charges q i and q separated by a distance r. 

Here we discuss a thermodynamic model appropriate to describe effects of strong association in dilute solutions. To have a definite example, consider a dilute electrolyte solution of a salt, say M X, that in solution dissociates to produce cations M of charge qu e and anions X of charge —qx e with aq [ = bqx- The interactions between these ions are composed of short-ranged interactions and long-ranged ionic interactions screened by the dielectric response of the solvent with dielectric constant e, as with r the distance between the ions. If the... 

Irish, D. E. (1971). Vibrational spectral studies of electrolyte solutions and fused salts. In Ionic Interactions from dilute solutions to fused salts, Vol. 2 (S. Petrrucci, ed.), New York Academic, pp. 188-258. 

There are several limitations which lead to the discrepancies in Tables IV-X. First of all, no model will be better than the assumptions upon which it is based. The models compiled in this survey are based on the ion association approach whose general reliability rests on several non-thermodynamic assumptions. For example, the use of activity coefficients to describe the non-ideal behavior of aqueous electrolytes reflects our uncertain knowledge of ionic interactions and as a consequence we must approximate activity coefficients with semi-empirical equations. In addition, the assumption of ion association may be a naive representation of the true interactions of "ions" in aqueous solutions. If a consistent and comprehensive theory of electrolyte solutions were available along with a consistent set of thermodynamic data then our aqueous models should be in excellent agreement for most systems. Until such a theory is provided we should expect the type of results shown in Tables IV-X. No degree of computational or numerical sophistication can improve upon the basic chemical model which is utilized. 

At the other end of the spectrum, Inverse sequences are observed for TiOj, a-FegOg and y-AljOg. Now the sites are the relatively small sRO groups which have a relatively strong electric field in their neighbourhood, and therefore prefer the smaller Ions. Thus, phenomenologically speaking, for site-adsorption the "like seeks like" rule seems to apply. This rule is also observed for ionic interactions in electrolytes, as expressed in the activity coefficients (sec. 1.5.4). 

The ionic interactions in a mixed electrolyte solution like seawater can affect the physical properties (density, heat capacity, etc.). Since the composition of natural waters can be quite different, it is useful to have models that can be used to describe how the ionic components affect the physical properties. This requires knowledge of ionic interactions in the solutions of interest. Over the years, a great deal of progress has been made in interpreting and modeling the physical-chemical properties of mixed electrolyte solutions (Millero, 2001). This has led to the development of models that can be used to estimate the properties of namral... 

In dealing with equilibria in natural waters, we wanted to give above all a feeling of the power of approach. In order not to overwhelm the reader with a large number of intricate details, we attempted to make nonideality corrections for electrolyte solutions simple and effective. The objective of this appendix is to review the various equilibria conventions usable for different natural water media—especially to compare the available conventions for describing (and measuring) pH and ionic equilibria in seawater—and to give an introduction to the ionic interaction theory, which is an expedient alternative and complementary approach to the ion association theory. 

Yu P, Zhou H, Mao LQ et al (2009) A facile approach to construction of a stable water-miscible ionic hquid/electrolyte interface with interactions between imidazolium moiety and carbon nanotubes. Electrochem Commun 11 1393-1396... 

The momentary association of simple ions is a well-known phenomenon that has been treated in a number of ways. For example, the ion association constant of Bjerrum has received much experimental support. However, the association of simple electrolytes is considered to be shortlived and has been included in the Debye-Hiickel electrostatic theory as correction constants to the concentration. On the contrary, the hydration of the ions may be long-lived. This may be accounted for by considering additionally the ionic interaction ... 

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