Metal dissolution free energy

The partial molar entropy of a component may be measured from the temperature dependence of the activity at constant composition the partial molar enthalpy is then determined as a difference between the partial molar Gibbs free energy and the product of temperature and partial molar entropy. As a consequence, entropy and enthalpy data derived from equilibrium measurements generally have much larger errors than do the data for the free energy. Calorimetric techniques should be used whenever possible to measure the enthalpy of solution. Such techniques are relatively easy for liquid metallic solutions, but decidedly difficult for solid solutions. The most accurate data on solid metallic solutions have been obtained by the indirect method of measuring the heats of dissolution of both the alloy and the mechanical mixture of the components into a liquid metal solvent.05... 

Factors Involved in Galvanic Corrosion. Emf series and practical nobility of metals and metalloids. The emf. series is a list of half-cell potentials proportional to the free energy changes of the corresponding reversible half-cell reactions for standard state of unit activity with respect to the standard hydrogen electrode (SHE). This is also known as Nernst scale of solution potentials since it allows to classification of the metals in order of nobility according to the value of the equilibrium potential of their reaction of dissolution in the standard state (1 g ion/1). This thermodynamic nobility can differ from practical nobility due to the formation of a passive layer and electrochemical kinetics. 

The electrochemical potential is a measure of the driving force (or free energy change) of the oxidation/reduction reactions that occur during metal dissolution. As mentioned, copper dissolution and redeposition may occur by the reduction-oxidation reaction ... 

Thermodynamically, dissolution should occur whenever the fiee energy of the solvated metal ion at a givai concentration is lower than the free energy of the atom in the metal, plus the thermodynamic potential of the electrons exchanged during the reaction via the standard hydrogen electrode. Such thermodynamic conditions arc summarized in the series of potential- H phase diagrams that have been extensively collated by Poutbaix [69]. Even in cases where a metal is coveted by a thin protective oxide, deleterious corrosion effects can... 

During the past few years, we have developed a method to combine our theory with DFT calculations [56, 57]. Basically, DFT provides several important parameters of our model, so that it has become possible to calculate free energy surfaces for the reactions and determine energies of activation. So far, our work has mainly been applied to electrocatalytic reactions, where we have focused on the effect of the electronic properties of the electrode on the reaction rate. However, the same procedure can be applied to metal deposition and dissolution, and we shall briefly return to this point at the end of this chapter. Here, we shall... 

DBC complexes with metal salts in the water-benzene system are the products of the interfacial reaction [119]. The measured work of adsorption (15.9 kJ/mol) can be taken as a sum of the free energy of complex formation and work of adsorption of DBC at the water-benzene interface. The dissolution of complexes in bulk phases was neglected. The interfacial constants of complex formation (Table 3) calculated from the work of adsorption are close to the constants determined in the mixed solvent - water-tetrahydrofuran [114]. The only exceptions are the complexes of DBC with Ba " and La salts. Apparently this is due to stronger Coulomb repulsion of ions in DBC-salt complexes at the interface as compared to the bulk phases. (At the interface, the anions... 

The mechanism of corrosion involves metal dissolution due to an electrochemical phenomenon. Thus, corrosion is associated with current flow over finite distances from the corroding metal and the amount of corrosion that can be accounted for is quantitatively determined by the amount of current passing through the metal. The electrochemical phenomenon occurs because of differences in potential between areas of the corroding metal surface. Therefore, the driving force of corrosion is the decrease in free energy associated with the formation of corrosion product on the metal surface, hi contrast, preventing corrosion leads to cathodic protection under steady-state conditions. 

The knowledge on the solubility of the crystalline substances formed and the identification of the ionic species are essential to the understanding of hydrothermal synthesis. As an example, the main equilibrium reactions for AlOOH dissolution in aqueous solution are shown in Table 1. For the estimation of metal oxides, the equilibrium constant K for each reaction is required. Equation (1) can be used for the estimation of the equilibrium constants under supercritical conditions. The data for equilibrium constants or Gibbs free energy changes and enthalpy of reaction for various reactions are available at ambient conditions. 

The reaction takes place spontaneously if the total change in the Gibbs free energy AG, including the oxide formation Gibbs free energy AGr and the possible dissolution of the cations in the metallic matrix. 

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