Mean oxidation number

A comparison of the mean oxidation numbers of the Al77 cluster 4 (+0.23) and the Al69 clusters 5 (+0.21) shows that in spite of a reduced number of A1 atoms, the reduction to metal has progressed further in the case of the Al69 cluster. 

The combination of TOC and COD measurements was used to introduce the MOC-concept of the mean oxidation number of carbon (Vogel et al., 2000). This concept may be useful to distinguish between oxidative, reductive and physical processes that are related to the diminution of the organic carbon content during water treatment. The MOC value is defined according to Equation 5-1. 

Vogel F, Hare J, Hug A, Rohr von PR (2000) The Mean Oxidation Number of Carbon (MOC)-A Useful Concept for Describing Oxidation Processes, Wat. Res. 34,... 

There are numerous complexes, mostly binuclear with metal—metal bonds, that can formally be described as having Pt111. Some compounds have a mean oxidation number of III while others contain Ptn and Pt , and it is often difficult to decide whether there is Pt11—Pt or Ptffl—Ptra. In other cases, the unpaired electrons may reside on the ligand rather than on the metal as in some bipyridyl and dithiolene complexes. 

Rabideau et al. confirmed the above qualitative results concerning the relative rates of HCIO4 and HCl reduction and found that the situation is complicated by the production of Cl in HCIO4 solutions and CI2 in HCl solutions. Also, if Br" is added to HCIO4 solutions, a net oxidation instead of reduction occurs if the mean oxidation number is initially approximately 4. 

The ability of N to exist in its compounds in at least 10 different oxidation states from —3 to +5 poses certain thermodynamic and mechanistic problems that invite systematic treatment. Thus, in several compounds N exists in more than one oxidation state, e.g. [N- "H4] + [N "02] , [N-" H4] + [N 03] , [N-"2H5] + [N 03]-, [N- "H4] + [N-3 3]-, etc. Furthermore, we have seen (p. 423) that, under appropriate conditions, NH3 can be oxidized by O2 to yield N2, NO or NO2, whereas oxidation by OCl yields N2H4 (p. 427). Likewise, using appropriate reagents, N2H4 can be oxidized either to N2 or to HN3 (in which the average oxidation number of N is — ). The thermodynamic relations between these various hydrido and 0x0 species containing N can be elegantly codified by means of their... 

Nitrogen cannot have an oxidation number lower than —3, which means that when NH3 takes part in a redox reaction, it always acts as a reducing agent. Ammonia may be oxidized to elementary nitrogen or to a compound of nitrogen. An important redox reaction of ammonia is that with hypochlorite ion ... 

To determine oxidation numbers, we assign each valence electron to a specific atom in a compound. This means that the oxidation number of an atom is the charge it would have if the compound were composed of ions. Ionic FeO, for example, would contain Fe cations and 0 anions. Thus, in FeO we assign iron an oxidation number of +2 and oxygen an oxidation number of-2. 

We can verify the electron counts by looking at oxidation numbers. The oxidation number of Fe increases by one, meaning that one electron must be released. The oxidation number of Cr changes from +6 to H-3, meaning that each Cr atom must gain three electrons. 

Thermal reduction at 623 K by means of CO is a common method of producing reduced and catalytically active chromium centers. In this case the induction period in the successive ethylene polymerization is replaced by a very short delay consistent with initial adsorption of ethylene on reduce chromium centers and formation of active precursors. In the CO-reduced catalyst, CO2 in the gas phase is the only product and chromium is found to have an average oxidation number just above 2 [4,7,44,65,66], comprised of mainly Cr(II) and very small amount of Cr(III) species (presumably as Q -Cr203 [66]). Fubini et al. [47] reported that reduction in CO at 623 K of a diluted Cr(VI)/Si02 sample (1 wt. % Cr) yields 98% of the silica-supported chromium in the +2 oxidation state, as determined from oxygen uptake measurements. The remaining 2 wt. % of the metal was proposed to be clustered in a-chromia-like particles. As the oxidation product (CO2) is not adsorbed on the surface and CO is fully desorbed from Cr(II) at 623 K (reduction temperature), the resulting catalyst acquires a model character in fact, the siliceous part of the surface is the same of pure silica treated at the same temperature and the anchored chromium is all in the divalent state. 

Ans. If you calculate the oxidation number assuming that the oxygen atoms are normal oxide ions, you get an answer +7, which is greater than the maximum oxidation number for sulfur. That must mean that one of the pairs of oxygen atoms is a peroxide, and thus the sulfur must be in its highest oxidation number, +6. The ion is peroxydisulfate ... 

There is now not only a great number but also a great variety of metal atom cluster compounds. In this essay I should like to discuss the differences between those that have metal atoms in a relatively high mean oxidation state (+2 to +4, and even, in rare cases, a bit higher) and those with metal atoms in oxidation states in the range -1 to +1. To keep the discussion within reasonable limits I shall restrict it almost exclusively to clusters consisting of only two or three metal atoms. I eschew the pedantic assertion that two atoms do not a cluster make. 

Care we write a formal charge with Arabic numerals, and means that the full charge exists as indicated Cu2+ means a copper atom with fully two electronic charges missing. We write an oxidation number with Roman numerals, and does not relate to any physical loss or gain of electrons it is purely a book-keeping exercise. Mnvn does not mean that a manganese atom has lost seven electrons. 

The metallic properties increase down any column and towards the left in any row on the periodic table. One important metallic property is that metal oxides are base anhydrides. A base anhydride will produce a base in water. These are not oxidation-reduction reactions. Many metal oxides are too insoluble for them to produce any significant amount of base. However, most metal oxides, even those that are not soluble in water, will behave as bases to acids. A few metal oxides, and their hydroxides, are amphoteric. Amphoteric means they may behave either as a base or as an acid. Amphoterism is important for aluminum, beryllium, and zinc. Complications occur whenever the oxidation number of the metal exceeds +4 as in the oxides that tend to be acidic. 

Does the fact that you can assign oxidation numbers of +1 to hydrogen and -2 to oxygen in water mean that water is an ionic substance Explain. 

For a number of years, phenolic substances were dosed by colorimetric techniques, based on redox reactions usually known as Folin Ciocalteau methods, even if a number of adjustments were developed to fit different matrix characteristics. The Folin Cioalteau reagent is a mixture of phosphomolybdic and phosphotingstic acids, with molybdenum in the 6+ oxidation state and, when the reaction takes place, it is reduced to form a complex called molybdenum blue and tungsten blue. In this complex, the mean oxidation state is between 5 and 6 and the formed complex is blue so it can be read spectrophotometrically at 750 nm. 

Oxidation always means an increase in oxidation number. Reduction always means a decrease in oxidation number. 

To answer the question determine the average oxidation numbers (ON) of the C atoms in reactant and in product. An increase (more positive or less negative) in ON signals an oxidation a decrease (more negative or less positive) signals a reduction no change means neither. 

The oxidation number, or oxidation state, is a bookkeeping device used to keep track of the number of electrons formally associated with a particular element. The oxidation number is meant to tell how many electrons have been lost or gained by a neutral atom when it forms a compound. Because oxidation numbers have no real physical meaning, they are somewhat arbitrary, and not all chemists will assign the same oxidation number to a given element in an unusual compound. However, there are some ground rules that provide a useful start. 

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