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Redox reactions electrode potentials

Half-cell reaction — The redox reaction (- electrode reaction) proceeding in a half-cell. The half-cell reaction changes the ratio of the activities of the reduced and oxidized forms. When the half-cell reaction is electrochemically reversible (see reversibility), the -> Nernst equation will describe the dependence of the -> electrode potential on the ratio of the activities of the reduced and oxidized forms. [Pg.323]

Since in a redox reaction electrons are transferred, and since electrons have charge, there is an electric potential E associated with any redox reaction. The potentials for the oxidation component and reduction component of a reaction can be approximated separately based upon a standard hydrogen electrode (SHE) discussed later in this lecture. Each component is called a hall reaction. Of course, no half reaction will occur by itself any reduction half reaction must be accompanied by an oxidation half reaction. There is only one possible potential for any given half reaction. Since tire reverse of a reduction half reaction is an oxidation half reaction, it would be redundant to list potentials for both the oxidation and reduction half reactions. Therefore, half reaction potentials are usually listed as reduction potentials To find the oxidation potential for the reverse half reaction, the sign of the reduction potential is reversed. Below is a list of some common reduction potentials. [Pg.113]

We have examined certain approaches to the investigation of redox reactions on membranes. Just as in the case of any electrode redox reaction, a potential arises on the membrane. In the simplest case the potential follows the Nernst equation. In other, more complex cases, when simultaneously ionic permeability is possible or when... [Pg.161]

The potential of a metallic electrode is determined by the position of a redox reaction at the electrode-solution interface. Three types of metallic electrodes are commonly used in potentiometry, each of which is considered in the following discussion. [Pg.473]

Redox Electrodes Electrodes of the first and second kind develop a potential as the result of a redox reaction in which the metallic electrode undergoes a change in its oxidation state. Metallic electrodes also can serve simply as a source of, or a sink for, electrons in other redox reactions. Such electrodes are called redox electrodes. The Pt cathode in Example 11.1 is an example of a redox electrode because its potential is determined by the concentrations of Ee + and Ee + in the indicator half-cell. Note that the potential of a redox electrode generally responds to the concentration of more than one ion, limiting their usefulness for direct potentiometry. [Pg.475]

Selecting a Constant Potential In controlled-potential coulometry, the potential is selected so that the desired oxidation or reduction reaction goes to completion without interference from redox reactions involving other components of the sample matrix. To see how an appropriate potential for the working electrode is selected, let s develop a constant-potential coulometric method for Cu + based on its reduction to copper metal at a Pt cathode working electrode. [Pg.497]

Determining Equilibrium Constants for Coupled Chemical Reactions Another important application of voltammetry is the determination of equilibrium constants for solution reactions that are coupled to a redox reaction occurring at the electrode. The presence of the solution reaction affects the ease of electron transfer, shifting the potential to more negative or more positive potentials. Consider, for example, the reduction of O to R... [Pg.528]

Oxidation Reactions. Potassium permanganate is a versatile oxidizing agent characterized by a high standard electrode potential that can be used under a wide range of reaction conditions (100,133—141). The permanganate ion can participate in a reaction in any of three distinct redox couples. [Pg.520]

Redox Potential the equilibrium electrode potential of a reversible reduction-oxidation reaction, e.g. Cu /Cu, Fe /Fe, Cl /Cr. [Pg.1372]

For an interfering redox reaction at an ion-selective membrane, the overpotential t B can be easily determined experimentally. It is the potential difference between the ion-selective membrane and an inert redox electrode in the same solution containing the measured ion and an interfering redox system. [Pg.242]

According to our analytical results on the solid-state redox reaction of LiNi02 based on the phenomenological expression for solid-state redox potentials of insertion electrodes [23], the reaction consists of three redox systems characterized by potentials of 4.23, 3.93, and 3.63V with re-... [Pg.330]

S.3.3 Electrocatalytic Modified Electrodes Often the desired redox reaction at the bare electrode involves slow electron-transfer kinetics and therefore occurs at an appreciable rate only at potentials substantially higher than its thermodynamic redox potential. Such reactions can be catalyzed by attaching to the surface a suitable electron transfer mediator (45,46). Knowledge of homogeneous solution kinetics is often used to select the surface-bound catalyst. The function of the mediator is to facilitate the charge transfer between the analyte and the electrode. In most cases the mediated reaction sequence (e.g., for a reduction process) can be described by... [Pg.121]

When the area A of the eleetrode/solution interface with a redox system in the solution varies (e.g. when using a streaming mercury electrode), the double layer capacity which is proportional to A, varies too. The corresponding double layer eharging current has to be supplied at open eireuit eonditions by the Faradaic current of the redox reaction. The associated overpotential can be measured with respect to a reference electrode. By measuring the overpotential at different capaeitive eurrent densities (i.e. Faradaic current densities) the current density vs. eleetrode potential relationship can be determined, subsequently kinetic data can be obtained [65Del3]. (Data obtained with this method are labelled OC.)... [Pg.271]

If a system is not at equilibrium, which is common for natural systems, each reaction has its own Eh value and the observed electrode potential is a mixed potential depending on the kinetics of several reactions. A redox pair with relatively high ion activity and whose electron exchange process is fast tends to dominate the registered Eh. Thus, measurements in a natural environment may not reveal information about all redox reactions but only from those reactions that are active enough to create a measurable potential difference on the electrode surface. [Pg.188]

The surface waves were simulated assuming the presence of two different functionalities, each undergoing a reversible two electron redox reaction. It was assumed that these surface functionalities were qulnones In Nernstlan equilibrium with the electrode potential before each DPV pulse. It was also assumed that the current during... [Pg.587]

In the case of redox reactions, polarization also depends on the natme of the nonconsumable electrode at which a given reaction occms (for the equilibrium potential, to the contrary, no such dependence exists). Hence, the term reaction will be understood as reaction occurring at a specified efectrode. ... [Pg.79]

It follows from the Franck-Condon principle that in electrochemical redox reactions at metal electrodes, practically only the electrons residing at the highest occupied level of the metal s valence band are involved (i.e., the electrons at the Fermi level). At semiconductor electrodes, the electrons from the bottom of the condnc-tion band or holes from the top of the valence band are involved in the reactions. Under equilibrium conditions, the electrochemical potential of these carriers is eqnal to the electrochemical potential of the electrons in the solution. Hence, mntnal exchange of electrons (an exchange cnrrent) is realized between levels having the same energies. [Pg.562]

Because of the excess holes with an energy lower than the Fermi level that are present at the n-type semiconductor surface in contact with the solution, electron ttansitions from the solution to the semiconductor electrode are facilitated ( egress of holes from the electrode to the reacting species ), and anodic photocurrents arise. Such currents do not arise merely from an acceleration of reactions which, at the particular potential, will also occur in the dark. According to Eq. (29.6), the electrochemical potential, corresponds to a more positive value of electrode potential (E ) than that which actually exists (E). Hence, anodic reactions can occur at the electrode even with redox systems having an equilibrium potential more positive than E (between E and E ) (i.e., reactions that are prohibited in the dark). [Pg.567]


See other pages where Redox reactions electrode potentials is mentioned: [Pg.15]    [Pg.68]    [Pg.89]    [Pg.979]    [Pg.598]    [Pg.466]    [Pg.474]    [Pg.108]    [Pg.354]    [Pg.246]    [Pg.295]    [Pg.243]    [Pg.331]    [Pg.4]    [Pg.61]    [Pg.87]    [Pg.267]    [Pg.269]    [Pg.412]    [Pg.152]    [Pg.86]    [Pg.1386]    [Pg.236]    [Pg.221]    [Pg.224]    [Pg.244]    [Pg.253]    [Pg.48]   
See also in sourсe #XX -- [ Pg.22 , Pg.23 ]




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