Silver , free transfer energy

This difference is a measure of the free-energy driving force for the development reaction. If the development mechanism is treated as an electrode reaction such that the developing silver center functions as an electrode, then the electron-transfer step is first order in the concentration of D and first order in the surface area of the developing silver center (280) (Fig. 13). Phenomenologically, the rate of formation of metallic silver is given in equation 17,... 

The reactivities of potassium and silver with water represent extremes in the spontaneity of electron-transfer reactions. The redox reaction between two other metals illustrates less drastic differences in reactivity. Figure 19-5 shows the reaction that occurs between zinc metal and an aqueous solution of copper(II) sulfate zinc slowly dissolves, and copper metal precipitates. This spontaneous reaction has a negative standard free energy change, as does the reaction of potassium with water ... 

In fact, each electron transfer half-reaction involves a free energy change following this formula. To reach the total variation in AG we sum the contributions of the two half-reactions, remembering that one is a reduction and the other an oxidation. For example, for the dissolution of silver chloride under standard conditions... 

For reasons already outlined, it is not possible to evaluate single-ion solvent activity coefficients, Vy-, with any degree of certainty. It is more satisfactory to choose one anion as a standard. We have chosen thiocyanate ion as a standard, and this leads to the linear free energy expressions (49) for solubilities of silver salts to (50) (cf. 29) for rates of reaction with methyl iodide and to (51) for acid strengths. In these equations, the value for an anion Y on transfer from DMF to... 

Salstrom, et al., J. Am. Chem. Soc., 58,1848 (1936)]. Calculate the activity and activity coefficient of the silver chloride at the various mole fractions. Determine the free energy of transfer of 1 mole of silver chloride from the pure fused state to the lithium chloride solution in which its mole fraction is 0.136, at 500 C. 

In aprotic solvents such as PC, DMSO, sulpholane, and DMF, silver chloride appears to be fairly soluble and forms complex ions such as AgClj whereas thallous chloride does not (see below). From the E°(I) values in water and in the aprotic solvent, the free energy of transfer (eqn. 2.6.35) gives the value for the transfer of 1 mole of LiCl. Once AG (LiCl) is known, the value for any cell involving the transfer of LiCl, such as cell (I), can be evaluated from eqn. 2.6.35 since E%T) is known when the solvent is water. The standard potential for cell (XI) (i.e. for M = Ag) may then be found from... 

Marcus (1987) defines me (base) sofmess parameter // for a solvent as me difference between the mean of me Gibbs free energies of transfer of sodium and potassium ions from water to a given solvent and me corresponding quantity for silver ion (/kJmol" ), divided by 1(X). He points out mat n is uncorrelated wim me p scale... 

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