Chemical potential strong electrolytes

For a strong electrolyte such as HC1 we assume that all of the electrolyte is dissociated to form the ionic species. In this case, it is appropriate to consider the chemical potential of the HC1 as the sum of the chemical potentials of the dissociated species. That isdd... 

The extreme nonidealities characteristic of electrolyte solutions warn of the dangers inherent in approximations commonly employed in general chemistry. Except in the crossover region of intermediate m where y + 1, blithe replacement of activity by molarity is seldom justified for strong electrolytes. Elementary treatments of acid dissociation, solubility products, and the like may therefore be subject to considerable error unless the realistic variations of chemical potential with concentration are properly considered. 

These equations are used whenever we need an expression for the chemical potential of a strong electrolyte in solution. We have based the development only on a binary system. The equations are exactly the same when several strong electrolytes are present as solutes. In such cases the chemical potential of a given solute is a function of the molalities of all solutes through the mean activity coefficients. In general the reference state is defined as the solution in which the molality of all solutes is infinitesimally small. In special cases a mixed solvent consisting of the pure solvent and one or more solutes at a fixed molality may be used. The reference state in such cases is the infinitely dilute solution of all solutes except those whose concentrations are kept constant. Again, when two or more substances, pure or mixed, may be considered as solvents, a choice of solvent must be made and clearly stated. 

The methods for obtaining expressions for the chemical potential of a component that is a weak electrolyte in solution are the same as those used for strong electrolutes. For illustration we choose a binary system whose components are a weak electrolyte represented by the formula M2A and the solvent. We assume that the species are M +, MA , A2-, and M2A. We further assume that the species are in equilibrium with each other according to... 

We consider only aqueous solutions here, but the methods used are applicable to any solvent system. The standard Gibbs energy of formation of a strong electrolyte dissolved in water is obtained according to Equation (11.28). In such solutions the ions are considered as the species and we are concerned with the thermodynamic functions of the ions rather than the component itself. We express the chemical potential of the electrolyte, considered to be MVtAv, in its standard state as... 

These equations can be expressed in terms of the chemical potentials of the salts when the usual definition of the chemical potentials of strong electrolytes is used. The transference numbers may be a function of x as well as the molality. Arguments which are not thermodynamic must be used to evaluate the integrals in such cases (see Kirkwood and Oppenheim [33]). One special type of cell to which either Equation (12.112) or Equation (12.113) applies is one in which a strong electrolyte is present in both solutions at concentrations that are large with respect to the concentrations of the other solutes. Such a cell, based on that represented in Equation (12.97), is... 

For a 1 1 strong electrolyte with ion pairing, the concentration of both ions is aMj, where a is the fraction of ion pairs that are dissociated, (putij = ,e, the extent of the dissociation reaction). The chemical potential and activity of such electrolytes are easily calculated, because, at equilibrium,... 

The chemical potential of a strong electrolyte, which may be assumed to be completely dissociated in... 

In the case of strong electrolytes, the chemical potential is the sum of the chemical potentials of the ions. For the simple case of a 1 1 electrolyte, the chemical potential is given hy... 

Similarly, the standard state of the strong electrolyte as a whole may be chosen so that its chemical potential in that state is equal to the sum of the chemical potentials of the ions in their respective standard states hence,... 

This result shows that the chemical potential of the weak electrolyte system may be expressed in terms of the activities of the ions only, without explicitly including the activity of the undissociated molecule. Equation (3.6.38) is no different in form from those for a strong electrolyte (equations (3.6.1) and (3.6.2)). Of course, the activities of the ions are much less for the weak electrolyte than those for the strong electrolyte for a given molality. Thus, on the basis of the present analysis for a weak electrolyte... 

The electrolyte flux is naturally affected by osmosis. Namely, a strong positive osmosis carries the electrolyte from the dilute solution to the concentrated one, which is incongruous salt flux. Conversely, electrolyte diffusion is retarded when the mobility of the co-ion is faster (negative osmosis). The flux of the solvent provides the energy required to transfer the electrolyte against its chemical potential gradient. 

In this chapter we discuss some of the properties of electrolyte solutions. In Sec. 12-1, the chemical potential and activity coefficient of an electrolyte are expressed in terms of the chemical potentials and activity coefficients of its constituent ions. In addition, the zeroth-order approximation to the form of the chemical potential is discussed and the solubility product rule is derived. In Sec. 12-2, deviations from ideality in strong-electrolyte solutions are discussed and the results of the Debye-Hiickel theory are presented. In Sec. 12-3, the thermodynamic treatment of weak-electrolyte solutions is given and use of strong-electrolyte and nonelectrolyte conventions is discussed. 

Application of the expression for the chemical potential of a strong electrolyte given by Eq. (12-10) to the system consisting of weak-electrolyte solute HA in a solvent yields the result... 

Neither the strong-electrolyte nor the nonelectrolyte formulation is applicable to weak electrolytes throughout the entire range of concentration. At high molality a weak electrolyte behaves like a nonelectrolyte and at low molality it behaves like a strong electrolyte. In order to develop expressions for chemical potentials of weak electrolytes which may be used over the entire composition range it is customary to resort to a nonoperational treatment based on certain structural considerations which involve nonmeasurable quantities. 

Here, in contrast to Eq. (12-3) in the strong-electrolyte case, the equality of chemical potentials is assumed to imply the existence of a chemical equilibrium. Since it is impossible to freeze the reaction [Eq. (12-38)] in order to study the components independently, the chemical-equilibrium assumption is nonoperational. 

In general, the chemical potential of the solution in the micellar phase must equal that in the surrounding aqueous medium when thermodynamic equilibrium is established. Nonpolar solutes, such as the permanent gases, which do not interact strongly with either phase may be distributed rather evenly over the whole microheterogeneous system (39). On the other hand, typical electrolytes are practically restricted to the aqueous medium, while molecules of hydrophobic substances, e.g. hydrocarbons, are almost totally sequestered in the micelles. 

If a transformation tends to run in one direction, this does not mean that the opposite direction is impossible, it just does not happen spontaneously. By itself, sand always trickles downward. A mole can shovel it upward, though, just as a harsh desert wind can pile it up into high dunes, but these processes do not occur spontaneously. Hydrogen and oxygen exhibit a strong tendency to react to form water. The reverse process never runs by itself at room conditions, but can be forced to do so in an electrolytic cell. Predicting substance transformations based upon chemical potentials always presupposes that there are no inhibitions to the process and that no outside forces are in play. We will gradually go into what this exactly means and what we need to look out for. 

An example of organic layer which changes its work function due to chemical modulation is electrochemically deposited polypyrrole. Because of its strong hydrogen bonding properties it binds water, alcohols, acetonitrile etc. It can be deposited under variety of conditions such as different deposition potential, different electrolyte, different solvents and additives. The result is a spectrum of materials which show different affinity to different chemical species. 

Chemical environment strongly influences transport. Adsorption and intercalation influence the potential distribution at the interface, affecting the tendency for electrons to accumulate in the film and the photovoltage. Composition of electrolyte influences rate of electron scavenging. Film history influences the density of traps and recombination centers. 

The chemical potentials of the strong electrolytes NaDS and NaCl in aqueous solution may be written as the sum of their ionic components, so that... 

The chemical potential of the solid crystal salt B is in phase equilibrium with the dissolved salt B in the liquid or aqueous phase. In aqueous systems we are primarily dealing with salts of strong electrolytes, which in water dissociate completely to the constituent cations and anions of the salt. The chemical potential of the dissolved salt is then given by... 

Otherwise, the intuitive assumption that the chemical potenfial of a strong electrolyte is equal to the sum of the chemical potentials of every ion component of the electrolyte is proven. The sum of the chemical potentials gives... 

At the Prague Institute of Chemical Technology, F. Jirsa studied anodic oxidation of gold [15] later he published an important paper about silver electrode for a silver-iron battery [16], Jaroslav Chloupek (1899-1975), partly with V. Danes (1907-1980) and B. Danesova, studied the electrode potential in solutions of mixed manganese salts [17], the solubility and activity coefficient of Ag2S04 in some solutions [18], the ions and deviations from the approximation of Debye-Hiickel theory [19], the liquid potentials [20], and the anomalous valency effect of strong electrolytes in aqueous solution [21]. 

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