Redox, definition

It appears that students avoid the electron transfer definition because the oxygen definition is more familiar. This definition has been learned in chemistry lessons using words in simple reaction equations. It has also made an impact due to the related experiments with sound and fire effects that can easily be recalled. The extended redox definition has perhaps been formally worked out on the blackboard but not necessarily intensified so that the electron transfer didn t cause a conceptual change in the cognitive structure. 

Oxygen and Oxidation Numbers. Redox definitions and oxidation numbers must finally come into play here in order to find students mental models appropriately. 

Further standard voltages could be measured and placed into an electrochemical sequence with other pairs of half-cells, as can be found in many chemistry teaching books. The extent of the introduction of the hydrogen half-cell as a standard electrode can be determined in each individual lesson. If one consequently describes all redox reactions in relation to the metal sequence, redox or electrochemical sequence with ions and offers the students model drawings (see Figs. 8.3 and 8.4), then the electron transfer and the redox definition, in terms of involved smallest particles, becomes even clearer and the mixing at the language level of substances and that of particles can be effectively suppressed. 

Using the electron transfer definition, many more reactions can be identified as redox (reduction-oxidation) reactions. An example is the displacement of a metal from its salt by a more reactive metal. Consider the reaction between zinc and a solution of copper(If) sulphate, which can be represented by the equation... 

Random copolymer—Distribution of the monomer units does not follow any definite sequence. These are produced in bulk, aqueous, suspension, or emulsion using free radical initiators of the peroxide type or redox systems. 

An oxidation half-reaction is a conceptual way of reporting an oxidation the electrons are never actually free. In an equation for an oxidation ha If-reaction, the electrons released always appear on the right of the arrow. Their state is not given, because they are in transit and do not have a definite physical state. The reduced and oxidized species in a half-reaction jointly form a redox couple. In this example, the redox couple consists of Zn2+ and Zn, and is denoted Zn2+/Zn. A redox couple has the form Ox/Red, where Ox is the oxidized form of the species and Red is the reduced form. 

As a result of strong electronic interactions between the two metalloporphyrin units, there is a substantial uncertainty in assigning oxidation states in mixed-valence group 2 complexes of redox-active metals, such as Co. Thus, although reduced neutral C02 derivatives can be reasonably well described as those of Co the location (metal versus porphyrin) of the electron hole(s) in the singly and doubly oxidized derivatives is not known definitively, and may be very sensitive to the medium [LeMest et al., 1996, 1997]. For example, in benzonitrile, the UV-vis spectmm of [(FTF4)Co2]" ... 

TABLE 2 Concentrations of Redox Products After the Electrolysis for 4 h by Applying a Definite E appi at the Stationary Interface Between W Containing 10 M H2O2 and DCE containing 10 M Tetrachlorohydroquinone, CQH2, Under the Deaerated Condition. As Supporting Electrolytes, 0.5 M Li2SO and 0.05 M TPenA+TEPB Were Added in W and DCE, Respectively. The pH of W Was Adjusted with the Aid of 0.1 M Phosphate Buffer to be 7.0... 

The generalization was based on the introduction of the concept of donor-acceptor pairs into the theory of acids and bases this is a fundamental concept in the general interpretation of chemical reactivity. In the same way as a redox reaction depends on the exchange of electrons between the two species forming the redox system, reactions in an acid-base system also depend on the exchange of a chemically simple species—hydrogen cations, i.e. protons. Such a reaction is thus termed proto lytic. This approach leads to the following definitions ... 

It is very often necessary to characterize the redox properties of a given system with unknown activity coefficients in a state far from standard conditions. For this purpose, formal (solution with unit concentrations of all the species appearing in the Nernst equation its value depends on the overall composition of the solution. If the solution also contains additional species that do not appear in the Nernst equation (indifferent electrolyte, buffer components, etc.), their concentrations must be precisely specified in the formal potential data. The formal potential, denoted as E0, is best characterized by an expression in parentheses, giving both the half-cell reaction and the composition of the medium, for example E0,(Zn2+ + 2e = Zn, 10-3M H2S04). 

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