Solutions ionic

The energy of ion-pair formation is the sum of attraction and repulsion energies. The attraction energy is the work of the Coulomb force from infinity to a distance d. The repulsive force results from the penetration of the electron clouds. For a pair of singly charged ions, the formation energy is [11] 

Ionic solutions are also prepared by dissolution of potential electrolytes in amphiprotic solvents. Pure amphiprotic solvents undergo self-dissociation, or autoprotolysis  

This reaction is characterized by an equilibrium constant (autoprotolysis constant 

The constants of several solvents are listed in Table III.3.7. Some examples of autoprotolysis are the reactions of water, methanol, acetic acid, and liquid ammonia  

2H3COH H3COH+ -h HsCO 2H3CCOOH H3CCOOH+ -h HsCCOQ-2NH3 NH+ -h NHJ 

A potential electrolyte HA may react with the solvent either as an acid  

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Gibbs equation of surface concentration This equation relates the surface tension (y) of a solution and the amount (T) of the solute adsorbed at unit area of the surface. For a single non-ionic solute in dilute solution the equation approximates to... 

The thennodynamic properties are calculated from the ion-ion pair correlation fimctions by generalizing the expressions derived earlier for one-component systems to multicomponent ionic mixtures. For ionic solutions it is also necessary to note that the interionic potentials are solvent averaged ionic potentials of average force ... 

Mayer J 1950 Theory of ionic solutions J. Chem. Phys. 18 1426... 

Friedman H L 1962 Ionic Solution Theory (New York Interscience)... 

Allnatt A 1964 Integral equations in ionic solution theory Mol. Phys. 8 533... 

Rasaiah J C 1970 Equilibrium properties of ionic solutions the primitive model and its modification for aqueous solutions of the alkali halides at 25°C J. Chem. Phys. 52 704... 

Chandler D and Andersen H C 1971 Mode expansion in equilibrium statistical mechanics II. A rapidly convergent theory of ionic solutions J. Chem. Phys. 54 26... 

Optimized convergence and application to ionic solution theory J. Chem. Phys. 55 1497... 

Ionic conductors arise whenever there are mobile ions present. In electrolyte solutions, such ions are nonually fonued by the dissolution of an ionic solid. Provided the dissolution leads to the complete separation of the ionic components to fonu essentially independent anions and cations, the electrolyte is tenued strong. By contrast, weak electrolytes, such as organic carboxylic acids, are present mainly in the undissociated fonu in solution, with the total ionic concentration orders of magnitude lower than the fonual concentration of the solute. Ionic conductivity will be treated in some detail below, but we initially concentrate on the equilibrium stmcture of liquids and ionic solutions. 

Modem-day approaches to ionic solutions need to be able to contend with the following problems ... 

However, for more complex fluids such as high-polymer solutions and concentrated ionic solutions, where the range of intemiolecular forces is much longer than that for simple fluids and Nq is much smaller, mean-field behaviour is observed much closer to the critical point. Thus the crossover is sharper, and it can also be nonmonotonic. 

J D and R H Fowler 1933. A Theory of Water and Ionic Solution, with Particular Reference to rdrogen and Hydroxyl Ions. Journal of Chemical Physics 1 515-548. 

For gases, pure solids, pure liquids, and nonionic solutes, activity coefficients are approximately unity under most reasonable experimental conditions. For reactions involving only these species, differences between activity and concentration are negligible. Activity coefficients for ionic solutes, however, depend on the ionic composition of the solution. It is possible, using the extended Debye-Htickel theory, to calculate activity coefficients using equation 6.50... 

A potential that develops at the interface between two ionic solutions that differ in composition, because of a difference in the mobilities of the ions ( ij). 

Liquid Junction Potentials A liquid junction potential develops at the interface between any two ionic solutions that differ in composition and for which the mobility of the ions differs. Consider, for example, solutions of 0.1 M ITCl and 0.01 M ITCl separated by a porous membrane (Figure 11.6a). Since the concentration of ITCl on the left side of the membrane is greater than that on the right side of the membrane, there is a net diffusion of IT " and Ck in the direction of the arrows. The mobility of IT ", however, is greater than that for Ck, as shown by the difference in the... 

As mentioned earlier, surfactants and ionic solutions significantly affect mass transfer. Normally, surface affects act to retard coalescence and thus increase the mass transfer. For example, Hikata et al. [Chem. Eng. J., 22, 61-69 (1981)] have studied the effect of KCl on mass transfer in water. As KCI concentration increased, the mass transfer increased up to about 35 percent at an ionic strength of 6 gi7i/l. Other investigators have found similar increases for hquid mixtures. 

The general equation can be further reduced to the case of infinite dilution limit, a binary mixmre, ionic solutions, and so on. These equations are supplemented by closure relations such as the Percus-Yevick (PY) and hypernetted chain (HNC) approximations. 

Technology Description Hydrolysis is the process of breaking a bond in a molecule (which is ordinarily not water-soluble) so that it will go into ionic solution with water. Hydrolysis can be achieved by the addition of chemicals (e.g., acid hydrolysis), by irradiation (e.g., photolysis) or by biological action (e.g., enzymatic bond cleavage). The cloven molecule can then be further treated by other means to reduce toxicity. 

A. Electro-osmosis in polar (nonionic) and ionic solutions 786... 

A. Electro-osmosis In Polar (Nonlonic) and Ionic Solutions... 

Electro-osmosis has been defined in the literature in many indirect ways, but the simplest definition comes from the Oxford English Dictionary, which defines it as the effect of an external electric held on a system undergoing osmosis or reverse osmosis. Electro-osmosis is not a well-understood phenomenon, and this especially apphes to polar non-ionic solutions. Recent hterature and many standard text and reference books present a rather confused picture, and some imply directly or indirectly that it cannot take place in uniform electric fields [31-35]. This assumption is perhaps based on the fact that the interaction of an external electric held on a polar molecule can produce only a net torque, but no net force. This therefore appears to be an ideal problem for molecular simulation to address, and we will describe here how molecular simulation has helped to understand this phenomenon [26]. Electro-osmosis has many important applications in both the hfe and physical sciences, including processes as diverse as water desahnation, soil purification, and drug delivery. 

S. Murad, R. Madhusudan, J. G. Powles. A molecular simulation to investigate the possibility of electro-osmosis in non-ionic solutions with uniform electric fields. Mol Phys 90 671, 1997 R. Madhususan, J. Lin, S. Murad. Molecular simulations of electro-osmosis in fluid mixtures using semi-permeable membranes. Eluid Phase Equil 150 91, 1998. 

Since the interface behaves like a capacitor, Helmholtz described it as two rigid charged planes of opposite sign [2]. For a more quantitative description Gouy and Chapman introduced a model for the electrolyte at a microscopic level [2]. In the Gouy-Chapman approach the interfacial properties are related to ionic distributions at the interface, the solvent is a dielectric medium of dielectric constant e filling the solution half-space up to the perfect charged plane—the wall. The ionic solution is considered as formed... 

In a recent publication [32] a more global approach of H has been suggested to describe the bulk properties of ionic solutions. We write... 

M. L. Japas, J. M. H. Levelt Sengers. Critical behavior of a conducting ionic solution near its consolute point. J Chem Phys 94 5361-5368, 1994. 

J. Stafiej, Z. Borkowska, J. P. Badiali. A simple description of the structure of ionic solutions at electrified interfaces. Cond Matt Phys (Ukraine) 72 51-61, 1997. 

Z. Borkowska, J. Stafiej, J. P. Badiah. Simple description of ionic solution at electrified interfaces. Proceedings of the Symposium on the Electrochemical Double Layer, Montreal, 1997, pp. 120-130. 

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