Metals reduction potentials

This order is always found for M = Mg, but not necessarily for M = Al, Cu, and Zn. In order to ensure that the required order is achieved, a complexing agent such as hexamethylphosphoramide (HMPA) or tris(3,6-dioxaheptyl)-amine (TDA-1) is added to render the metal reduction potential more negative. 

Other Substrates Deposition of cadmium was also studied on Bi, Sn and Pb [303], Ni [304], reticulated vitreous carbon [305], Ti [306], and indium tin oxide [307]. UPD of Cd on tellurium results in CdTe formation [270, 308]. Electrodes coated with conducting polymers were also used to deposit cadmium electrochemi-cally. In the case of polyaniline, the metal reduction potential corresponds to the neutral (nonconducting) state of the polymer, therefore cadmium was found to deposit on the substrate-glassy carbon electrode surface, in the open pores of the polymer film [309, 310]. 

To improve the PEFC cathode durability, both materials and system approaches have been proposed in the last years. From the system point of view, improvements in cathode durability can be achieved by minimizing the residence time of the hydrogen-air front in the anode compartment. On the materials side, Pt alloys have shown higher durability compared relative to Pt-based electrodes [34]. However, since transition metal reduction potential is below that of hydrogen. 

Thennodynamic stability is generally provided for noble metals in most media as tlieir oxidation potential is more anodic tlian tire reduction potential of species commonly occurring in tire surrounding phase. However, for many materials of technological and industrial importance tliis is not tire case. 

Divalent copper, cobalt, nickel, and vanadyl ions promote chemiluminescence from the luminol—hydrogen peroxide reaction, which can be used to determine these metals to concentrations of 1—10 ppb (272,273). The light intensity is generally linear with metal concentration of 10 to 10 M range (272). Manganese(II) can also be determined when an amine is added to increase its reduction potential by stabili2ing Mn (ITT) (272). Since all of these ions are active, ion exchange must be used for deterrnination of a particular metal in mixtures (274). 

Although it is only slowly oxidized in moist air at ambient temperature, cadmium forms a fume of brown-colored cadmium oxide [1306-19-0] CdO, when heated in air. Other elements which react readily with cadmium metal upon heating include the halogens, phosphoms, selenium, sulfur, and tellurium. The standard reduction potential for the reaction... 

Q Zeng, ET Smith, DM Kurtz, RA Scott. Protein determinants of metal site reduction potentials. Site directed mutagenesis studies of Clostridium pasteurianum laibredoxin. Inorg Chim Acta 242 245-251, 1996. 

Various other observations of Krapcho and Bothner-By are accommodated by the radical-anion reduction mechanism. Thus, the position of the initial equilibrium [Eq. (3g)] would be expected to be determined by the reduction potential of the metal and the oxidation potential of the aromatic compound. In spite of small differences in their reduction potentials, lithium, sodium, potassium and calcium afford sufficiently high concentrations of the radical-anion so that all four metals can effect Birch reductions. The few compounds for which comparative data are available are reduced in nearly identical yields by the four metals. However, lithium ion can coordinate strongly with the radical-anion, unlike sodium and potassium ions, and consequently equilibrium (3g) for lithium is shifted considerably... 

A major advance in the art of effecting Birch reductions was the discovery by Wilds and Nelson that lithium reduced aromatic steroids much more efficiently than had hitherto been possible with sodium or potassium. The superiority originally was attributed to the somewhat higher reduction potential of lithium as compared to the other alkali metals. Later work showed that the following explanation is more probable. ... 

Be is much less than that of its congeners, again indicating its lower electropositivity. By contrast, Ca, Sr, Ba and Ra have reduction potentials which are almost identical with those of the heavier alkali metals Mg occupies an intermediate position. 

Alkali and alkaline-earth metals have the most negative standard reduction potentials these potentials are (at least in ammonia, amines, and ethers) more negative than that of the solvated-electron electrode. As a result, alkali metals (M) dissolve in these highly purified solvents [9, 12] following reactions (1) and (2) to give the well-known blue solutions of solvated electrons. 

The oxidation-reduction potentials of metal complex ions. D. D. Perrin, Rev. Pure Appl. Chem., 1959, 9, 257-285 (111). 

A student was given a standard Cu(s) Cu2+(aq) half-cell and another half-cell containing an unknown metal M immersed in 1.00 M M(NO,)2(aq). When the copper was connected as the anode at 25°C, the cell emf was found to be —0.689 V. What is the reduction potential for the unknown M2+/M couple ... 

In damp air, materials with standard reduction potentials less than 0.88 V oxidize spontaneously. Atmospheric O2 easily oxidizes iron and aluminum, the most important structural metals ... 

C19-0134. Use standard reduction potentials from Table 19-1 and Appendix F to determine. sp for as many metal hydroxides as the table allows. Compare your values with those in Appendix E. If there are. sp values for hydroxides in Appendix E that cannot be calculated from standard reduction potentials in Appendix F, use the. STjp values to calculate the appropriate standard reduction potentials. 

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