Stoichiometries oxidation

Copper would therefore be expected to form a protective film, be it of copper(I) or copper(II) oxide. (Note, however, that the picture becomes confused where two oxide stoichiometries are involved.) Indeed, oxidation of Cu at 600 to 800 °C proceeds according to the parabolic law ... 

A particular feature of metal oxide surfaces is that, depending on the oxide stoichiometry and the specific surface, surface cell dimensions may be quite large. In Ti02 rutile (110), for example, it is 6.49 A between neighbouring 5-fold surface Ti atoms in the (lTO) direction. For a small adsorbate which adsorbs preferentially on metal atoms, this may largely exclude direct adsorbate-adsorbate interactions in certain directions. A comparison of some atomic distances with proposed binding modes for formic acid on some examples of metal oxide surfaces are presented in Table 8. 

Bulk oxide stoichiometries depend strongly on oxygen pressure, a fact that has been recognized for a long time and we have alluded to above [10]. So do oxide surfaces, structures and stoichiometries, a fact that has been shown again in a recent study on the Fe203(0001) surface by the Scheffler and Schlogl... 

Figure 1.41 Defect state concentration No determined by Schottky-Mott analysis of capacitance curves and corresponding Nb oxide stoichiometry as a function of the formation potential...

The use of zeolite-hosted semiconductor oxides as chemicai sensors towards oxidizing or reducing gases might be attractive. Since the alteration of the conductivity depends on changes of the oxide stoichiometry [93,94], shorter diffusion distances in smaller clusters should result in shorter response times of the sensors. Fast response is a prerequisite for the application of sensors based on changes of the bulk composition, e.g. in air/fuel ratio control devices. 

The P450 oxidation stoichiometry requires one molecule of oxygen and two electrons fi om NAD(P)H to add one oxygen atom to a substrate. If the ratio of reduced pyridine nucleotide (or oxygen) consumed to product formed is greater than one, the enzyme is said to be uncoupled. Uncoupling occurs when (a) the ferrous dioxy complex reverts to the ferric state by dissociation of superoxide. 

The paper presents data on development of Mn oxide catalysts for selective oxidation of lean methane mixtures with air to produce CO2 and generate heat. To obtain catalysts, new approaches to the synthesis of polyoxide materials based on Mn were adopted. Catalysts were modified by doping with La, Ce, Ba and Sr nitrates which were deposited from solutions onto the stabilized 2%Ce/0-Al2O3 support (of surface area 100 m /g and pellet diameter 4-5 mm). By varying the components of the impregnation mixture, it was possible to optimize the chemical composition and ratio of elements in the multi-component catalysts (at Ba Sr La Ce Mn = 1 1 1 7 10 ratio). The catalyst composition conformed to the oxide stoichiometry in the perovskite structure. 

Measurements of Fe(II)/02 oxidation stoichiometry have been made with an oxygen electrode for the oxidation of 48 Fe(II) atoms per apoferritin molecule. Ratios... 

The photolysis of DMSO was studied in detail by Gollnick and Stracke [12,133,134], though it was mentioned preliminarily in previous studies [21,135], Photolysis of solutions of DMSO in water, alcohols, or acetonitrile results in a variety of products. The reactions are done at high concentrations of DMSO (1-2 M), and it is reasonable to expect that sulfenic and sulfinic acids are further oxidized to the sulfonic acid by its presence. A careful accounting of the oxidation stoichiometry [12], however, shows that additional Me2S is formed by another mechanism. 

The reaction between HN3 and [Mn(bipy)2(H20) ] was followed spec-trophotometrically at 400 nm. The reaction shows an initial increase in absorbance followed by a decrease to zero, which may be explained by the formation of two 1 1 complexes with NJ. Both these complexes, [Mn(bipy)2(N3)] and [Mn(bipy)2(OH)(N3)], are involved in the oxidation process, producing N3 free radicals. The oxidation stoichiometry confirms the overall reaction as in equation... 

The fractions of the 1-ethoxyethoxy radicals undergoing reactions 1-4 are shown in Tables and compared with previous FllR studies and with theoretical estimates. Although diethyl ether is rapidly photo-oxidised, its contribution to tropospheric ozone formation is limited as one of the major products is ethyl formate which is relatively unreactive in the troposphere. This is also confirmed from the NO-NO2 oxidation stoichiometry, ca, 1 mole NO is oxidised per mole diethyl ether reacted. 

The potential recorded as a function of time yields a transient similar to the one shown in Figure 6.18. A potential plateau is observed, which corresponds to the reduction of the oxide. In the absence of important kinetic effects, the plateau potential is determined by the reversible potential of oxide formation and therefore, in principle, permits to identify the oxide stoichiometry. The charge for oxide reduction is proportional to the length of the plateau. This permits to estimate the film thickness provided one knows the reaction stoichiometry and the density of the film. 

When ethane is pyrolyzed in the presence of small oxygen quantities, it primarily produces more ethylene than hydrogen this is due to the oxidation stoichiometry ... 

The transplutonium oxides are useful for studying crystal-field effects or interactions, as the dioxides and the C-type sesquioxides have cubic symmetry and both oxide stoichiometries are available for most of the oxides. The magnetic behavior of these transplutonium oxides is compared with their lanthanide counterparts in section 3. The behavior of individual oxides is discussed briefly here and data are provided in table 28. 

The actinides are probably more like the lanthanides in their oxide forms than in the solid phases of their other compounds. This is especially true when considering the metallic states, where large deviations are apparent. If an actinide exists in a particular oxide stoichiometry (e.g., a sesquioxide), it is likely to have comparable chemical and physical behavior to that of a lanthanide sesquioxide that has a similar ionic radius. The first important point for these two series of oxides is whether a particular stoichiometry is formed by different members of each series. 

A comparison of oxides is shown in fig. 15 which compares and summarizes, in a simple fashion, the oxide formation behavior for the two series of elements. It is obvious that, excluding the behavior of Pa, U and Np, the actinides show a greater tendency for variable oxide stoichiometries than do the lanthanides. The most striking difference (besides the fact that the elements Pa through U form oxides above the dioxide) is that all the actinides from Th through Cf form dioxides, while lanthanide dioxides are known only for Ce, Pr and Tb (the dioxides of Pr and Tb are more difficult to form). Only two oxide stoichiometries are shown for Ce and Pu in fig. 15. In reality, oxides with O/M ratios between 1.5 and 2.0 are known for both elements, although those for... 

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