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Redox Potential importance

TABLE 2.1 Redox Potentials Important for Selected Microbiological Processes (Madigan et a ., 2000). The Potentials are given under Standard Conditions, i.e., at pH = 7, 25°C, 1 atm and 1 Molar Concentration of Relevant Components... [Pg.15]

Another perspective that deserves to be further explored concerns the application of the redox potential parameterization models to the prediction (estimate) of the redox potential of complexes. This can be of a relevant identification significance of unknown compounds, by comparing the predicted and the measured values of the redox potential. Important cases of application can include the identification in situ of reaction intermediates or products without requiring their isolation. [Pg.687]

Other important effects of ligand and pH changes on redox potentials will be given under the appropriate element. [Pg.102]

Two important redox potentials for reduction by sulphur dioxide in aqueous solution are ... [Pg.291]

Nitric oxide and NjO are direct intermediates in the denitrification pathway, the reduction of NO3 to Nj. Reduction to Nj is often incomplete, so that both NjO and Nj are equally important end products of denitrification, the ratio of NjO/Nj production being determined by soil physical properties. For example, NjO is the main end-product in acid soils, whereas low redox potentials and high organic matter content favour the further reduction to Nitric... [Pg.71]

The free energy changes of the outer shell upon reduction, AG° , are important, because the Nernst equation relates the redox potential to AG. Eree energy simulation methods are discussed in Chapter 9. Here, the free energy change of interest is for the reaction... [Pg.403]

An effective method for localizing causes of redox potentials is to plot the total backbone and side chain contributions to ( ) per residue for homologous proteins as functions of the residue number using a consensus sequence, with insertions treated by summing the contribution of the entire insertion as one residue. The results for homologous proteins should be examined for differences in the contributions to ( ) per residue that correlate with observed redox potential differences. These differences can then be correlated with any other sequence-redox potential data for proteins that lack crystal or NMR structures. In addition, any sequences of homologous proteins that lack both redox potentials and structures should be examined, because residues important in defining the redox potential are likely to have semi-sequence conservation of a few key amino acid types. [Pg.407]

One example of a sequence determinant of redox potentials that has been identified in this manner is an Ala-to-Val mutation at residue 44, which causes a 50 mV decrease in redox potential (and vice versa) in the rubredoxins [68]. The mutation was identified because the sum of the backbone contributions to ( ) of residues 43 and 44 change by 40 mV due to an —0.5 A backbone shift away from the redox site. This example points out the importance of examining the backbone contributions. The corresponding site-specific mutants have confirmed both the redox potential shift [75] and the structural shift [75]. [Pg.407]

Obtain all available information about the material. If it is a surplus or off-specification product, obtain an analysis or a Material Safety Data Sheet. If it is a waste, check for previous analyses, and if none exists, obtain one. (Even if a previous analysis exists, consider running a few screening-type field analyses for confirmation of important properties such as pH, redox potential, or other oxidizer test such as cyanide, sulfide, and flashpoint.)... [Pg.179]

In view of the importance of the hydronium ion, HjO, and dissolved oxygen as electron acceptors in corrosion reactions, some values of the redox potentials E and chemical potentials n for the equilibria... [Pg.60]

It is usual to choose a container metal for fused salts sufficiently noble for the displacement reaction (2.16) to be negligible, and the most important aspects of corrosion are, as in aqueous solutions, those which involve reducible impurities, although in a salt melt there is also the additional possibility of a reducible anion (see above). All such factors can be described as controlling the oxidising power of the melt, which can be defined in terms of a redox potential just as in aqueous solutions The redox potential is expressed by relationships of the form... [Pg.436]

A further important feature of HMPA is its stabilizing effect on the Redox potential of [Fe(CO)4]2 by ion solvation. In less polar solvents, electron-transfer reactions take place and [Fe(CO)4]2 is oxidized to [HFe3(CO)iThis redox reaction is suppressed in HMPA. [Pg.12]

Similar effects are observed in the iron complexes of Eqs. (9.13) and (9.14). The charge on the negatively charged ligands dominates the redox potential, and we observe stabilization of the iron(iii) state. The complexes are high-spin in both the oxidation states. The importance of the low-spin configuration (as in our discussion of the cobalt complexes) is seen with the complex ions [Fe(CN)6] and [Fe(CN)6] (Fq. 9.15), both of which are low-spin. [Pg.179]

It is important to note that the PMF is usually expressed in millivolts, and AG as kJ mor. The redox potential difference AE (where AE, = EhA - EhB between two redox couples Arej/Ao and Bred/Bo is often expressed in electrical units, but it can also be expressed as kJ mof ... [Pg.148]

In addition to effects on the concentration of anions, the redox potential can affect the oxidation state and solubility of the metal ion directly. The most important examples of this are the dissolution of iron and manganese under reducing conditions. The oxidized forms of these elements (Fe(III) and Mn(IV)) form very insoluble oxides and hydroxides, while the reduced forms (Fe(II) and Mn(II)) are orders of magnitude more soluble (in the absence of S( — II)). The oxidation or reduction of the metals, which can occur fairly rapidly at oxic-anoxic interfaces, has an important "domino" effect on the distribution of many other metals in the system due to the importance of iron and manganese oxides in adsorption reactions. In an interesting example of this, it has been suggested that arsenate accumulates in the upper, oxidized layers of some sediments by diffusion of As(III), Fe(II), and Mn(II) from the deeper, reduced zones. In the aerobic zone, the cations are oxidized by oxygen, and precipitate. The solids can then oxidize, as As(III) to As(V), which is subsequently immobilized by sorption onto other Fe or Mn oxyhydroxide particles (Takamatsu et al, 1985). [Pg.390]

Therefore, polysulfide ions play a major role in the global geological and biological sulfur cycles [1, 2]. In addition, they are reagents in important industrial processes, e.g., in desulfurization and paper production plants. It should be pointed out however that only sulfide, elemental sulfur and sulfate are thermodynamically stable under ambient conditions in the presence of water, their particular stabihty region depending on the redox potential and the pH value [3] ... [Pg.128]

The importance of hydrogen bonds for the redox potential of the Rieske cluster has been demonstrated by site-directed mutagenesis of... [Pg.110]

Late transition metal or 3d-transition metal irons, such as cobalt, nickel, and copper, are important for catalysis, magnetism, and optics. Reduction of 3d-transition metal ions to zero-valent metals is quite difficult because of their lower redox potentials than those of noble metal ions. A production of bimetallic nanoparticles between 3d-transi-tion metal and noble metal, however, is not so difficult. In 1993, we successfully established a new preparation method of PVP-protected CuPd bimetallic nanoparticles [71-73]. In this method, bimetallic hydroxide colloid forms in the first step by adjusting the pH value with a sodium hydroxide solution before the reduction process, which is designed to overcome the problems caused by the difference in redox potentials. Then, the bimetallic species... [Pg.53]


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