Oxidation reactions half reaction

A summary of oxidation-reduction half-reactions arranged in order of decreasing oxidation strength and useful for selecting reagent systems. 

Oxidation A half-reaction in which there is an increase in oxidation number, 88 chromium, 548 electrolysis and, 498 fluorine, 557 halogens, 557-558 oxoacids, 568-570 oxoanions, 568-570 species strength, 506-507q transition metals, 546t zinc, 86-87... 

The left half of this electrochemical cell, containing a zinc electrode and zinc sulfate solution, engages in an oxidation reaction. This reaction liberates electrons and turns zinc atoms into zinc ions (Zn, which is a zinc atom that has lost two electrons and therefore has a net positive charge of 2). The zinc atoms come from the electrode, which is gradually depleted the zinc ions that are produced in the reaction enter the solution. In the right half of the cell, a reduction reaction occurs electrons combine with copper ions to produce neutral atoms of copper. Copper ions leave the solution in the process and collect at the copper electrode. Over time, the zinc electrode and copper solution will run out of material, causing the reaction to cease unless the material is replenished. 

Show the reaction of iron with a hydrochloric acid solution to produce H2 gas by using the oxidation-reduction half-reaction method. 

Mole relationships apply to electrons in balanced oxidation-reduction half-reactions. 

In the equation, silver is being reduced and iron is being oxidized. The half-reactions would be set up as follows ... 

TABLE 16.3 Selected Standard Electrode Potentials for Oxidation-Reduction Half Reactions... 

Must two oxidation-reduction half-reactions be carried out (a) in the same location and (b) at the same time ... 

The principle described in this section is very useful, but it must be applied with some caution. For example, in the electrolysis of an aqueous solution of sodium chloride, we should be able to use %° values to predict which products are expected. Of the major species in the solution (Na+, Cl-, and H20), only Cl- and H20 can be readily oxidized. The half-reactions (written as oxidation processes) are ... 

STANDARD REDUCTION POTENTIALS OF SOME OXIDATION-REDUCTION HALF-REACTIONS ... 

Table I. Some Oxidation-Reduction Half-Reactions for the Species Shown in...

Use the following reaction to define redox reaction, half-reaction, oxidizing agent, reducing agent ... 

Sketch a galvanic cell that makes use of this reaction. Which metal ion is reduced Which metal is oxidized What half-reaction takes place at the anode in the cell What half-reaction takes place at the cathode ... 

Although FMO and cytochrome P450 are involved in similar oxidation reactions, the reaction mechanism by FMO is radically different from that of cytochrome P450. Most importantly, the reactive hydroxyperoxyflavine is unusually stable with a rather long half-life and does not require the presence of the substrate to be oxidized. By contrast to cytochrome P450, the activated form of FMO is already present before introduction of the substrate. 

Oxidation-reduction half-reactions were discussed in Section 4.10. 

The equilibrium constant, K, can - in principle - be determined from the free energies of formation of the reactants and products through the relationship between AG° and K. However, since free electrons do not exist in aqueous solution, chemists have devised a way of eliminating the free electron from the reaction. Half-reactions of the sort shown in eqn [1] are combined with with the oxidation of H2(g) to H" (aq). This reaction releases one electron and is defined to have a free energy change of 0. Some algebraic manipulation will show that this combination of... 

Reactions occurring during corrosion are conveniently divided into those taking place at the anode and those taking place at the cathode. The reactions may be (and usually are) more extensive and complex than the primary oxidation reduction half-reactions. Let us consider the corrosion of a piece of iron pipe. The basic galvanic cell is illustrated in Fig. 7-12. 

William S. Knowles (United States) and Rybji Noyori (Japan) for their work on chirally catalyzed hydrogenation reactions and K. Barry Sharpless (United States) for his work on chirally catalyzed oxidation reactions. Half of this prize was awarded to Knowles and Noyori for their work with chiral catalysts that chirally catalyzed hydrogenation reactions, or reactions in which two hydrogen atoms are added. This work found applications in pharmaceutical production soon after its discovery. Sharpless was awarded the other half of this prize for developing chiral catalysts to carry out oxidation reactions, which represent another important class of reactions in organic synthesis. 

Relating standard emf to standard reduction potentials of the reduction (cathode) and oxidation (anode) half-reactions [20.11 ] Relating free-energy change and emf... 

Such a transformation is called an oxidation-reduction half-reaction or a redox halfreactionIt concerns two species for which a given element exists under two different forms. These two species are called the oxidant (or oxidizing agent) and the reductant (or reducing agent) denoted by Ox and Red respectively. They make up a redox couple usually denoted by Ox/Red. 

Film homogeneity is enhanced if the oxidant s half-reaction does not evolve gas. 

The Status of the Hydrogen Electrode. Probably no area of electrochemistry is more greatly neglected in current texts than the history of the choice of the hydrogen electrode as the reference standard for electromotive force measurements. Since all tables of potentials of oxidation-reduction half-reactions are based on the half-cell reaction 35H2=H +e , it would seem that the selection of this reaction as the standard should warrant more attention. If the selection is treated at all, it is usually dismissed as an arbitrary choice, which it is, with no reference made to the people and events involved in establishing this fundamental reference point for the EMF scale. One possible exception may be noted ( ). The referenced edition of this work is perhaps the best previously existing source on this topic. However, the subsequent edition omits the subject entirely. 

Because this is an oxidation, the half-reaction with the mote negative value of E°ed is favored. We therefore expect Ni(s) to be oxidized at the anode. We can summarize the electrode reactions as follows ... 

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