Electrode potentials determination

Figure 7. A plot of the logarithm of the ratio k /N against the electrode potential determined for the (311) surface.

Although a single value is given in Table 16 for Ee (Ce3+(aq)/Ce4+(aq)), the oxidation potential of Ce3+ ion in aqueous media varies considerably with the nature of the counterion, doubtless due to stabilization of Ce4+ to different extents by complexation. Thus in 1M H2S04, Ee= 1.4435 V,680 but in perchloric acid solutions, = 1.6400-1.7310 V depending on concentation,681 while a range of 1.6085-1.6104 V was observed in nitric acid solutions.682 There is some evidence for the formation of polymeric species in aqueous nitric acid solutions, and this may explain some anomalies in electrode potential determinations. Values for association constants of 17 and 2 respectively for Ce4+-Ce4+ and Ce4+-Ce3+ interactions were obtained.683... 

Equilibrium electrode potential — is the value of -> electrode potential determined exclusively by a single redox system ox/red in the absence of current and under complete equilibration. The rates of ox to red reduction and of red to ox oxidation processes are equal under these circumstances (see exchange current density). The value of equilibrium e.p. is determined by the - Nernst equation. Equilibrium e.p. presents a - redox potential in its fundamental sense. See also - reversibility. 

The electrode potential determines which electrode reaction may occur an electrolytic reaction can be controlled by means of the potential until and including the potential-determining step. The potential also governs the relative rate of an electron transfer and a competing chemical reaction thus affecting the product distribution in a branched reaction. Other factors, such as orientation of molecules at the electrode,30 may be potential-dependent. 

The potential of an electrode gives essential information about the phenomena being observed at the electrode. The electrode potential determines both direction and rate of the electrode reaction. Therefore it is necessary to measure or control the electrode potential against a reference electrode, of which the potential is stable and reproducible during a series of measurements. In aqueous solutions there are several such well-established reference electrodes, namely Ag/AgCl, Hg/Hg2Cl2,... 

Chemistry Video Consortium, Practical Laboratory Chemistry, Educational Media Film and Video Ltd, Harrow, Essex, UK - Electrochemical techniques (using galvanic cells, using conductometric cells, determining standard electrode potentials, determining solubility products, thermodynamic characteristics of cells, conductometric titrations and using an automatic titrator). 

Electrode Potential Determination Illustration with Calomel Electrode Hydrogen... 

Classical electrochemistry on metal electrodes, or as Bockris1 defined it, electrodics, operates, as a rule, with the electrode potential, determined in the simplest case by a single reaction, called the potential-determining reaction. 

Figure 34a and b plot 0s(CH2) and 0as(CH2> as functions of the electrode potential determined using this procedure. 

Table 9.14 summarizes data obtained for Co-Cr, 316L stainless steel and titanium. The type of electrochemical technique used has an important influence on the results, which might indicate that the electrode potential determines the beneficial or detrimental effect of proteins on corrosion. 

The prevailing electrode potential determines the direction and rate of the electrode reactions. For example, in a 1 molar solution of Fe " and Fe ions that is in contact with a platinum electrode, the electrode reaction (1.13) takes place. 

The voltage dependence of the adsorption of neutral molecules is obviously connected with the interaction studied by A. N. Frumkin between the adsorption energy of a surface-active molecule and the value of the electrode potential determined by the surface eharge. The zero charge potential in... 

Because of the relationship between the electrode potential-determining species and the electrode potential, electrodes may be employed as sensors (ion-sensitive and -selective detectors) in analytical chemistry, medicine, process control, and environmental monitoring. 

Chapter 2 discusses various theoretical models of polymer-based electrocatalytic systems. The discussion concentrated on an analysis of the steady-state current response. Time-dependent current responses are not considered. We have shown that the response of polymer-based electrocatalytic systems can be quantified in terms of very simple theoretical models. These models yield on analysis simple expressions for the current response involving experimentally quantifable parameters, such as layer thickness, catalyst-loading, and electrode potential. Determining reaction orders with respect to the latter parameter enables us to identify the kinetic case unambigously. Furthermore we have shown that kinetics can be conveniently represented in terms of pictorial case diagrams, which can be used in mechanistic diagnosis. 

Hydrogen electrodes are difficult to use in many pH determinations and either Ag-AgCl or calomel reference electrodes are usually used A typical pH-measurement reference electrode is shown in Figure 5.12c. Thus we establish a cell in which glass-electrode potential is compared with the potential of a nonhydrogen reference electrode which in turn has an electrode potential determined against a hydrogen reference. The cell which is formed by the two electrodes used in a pH measurement is then described by... 

The electrodiC potential determines which electron transfer reactions can occur and also their absolute (and relative) rates, i.e, current densities. The potential, or current density is in many cases a major factor controlling the current efficiency, the space-time yield and the product quality. 

The examples in Section 1.8.1 to 1.8.3 show the complex concurrence of the cell reaction and secondary reactions that often characterizes a battery, since electrochemical reactions are independent from each other and only the electrode potential determines whether they occur or not. As a consequence, the cell reaction and its parameters are not sufficient to describe the behavior of a battery system instead many further parameters influence parameters influence its performance. 

Further, it is proposed that these symbols precede the basic symbol of EA as a left subscript, in the manner presented in Table 5. Now, both the symbol and the full name of any particular experimentally accessible EA of electrode reactions must by rather extensive, to avoid any confusion in identification of the EA. For instance, islf Ec) (see Table 5) is named as follows energy of activation at constant cathodic electrode potential, determined in the isothermal cell without transference. Because the use of such definitions to describe the pertinent EA for the reaction studied under specified experimental conditions is cumbersome, it is useful to introduce appropriate abbreviations. Thus, in the above-mentioned example, the abbreviation proposed is w-EACEP-c. Such abbreviations cannot be shortened further if full information concerning the EA is to be instantly conveyed. 

Electromotive series A serial arrangement of metallic elements or ions according to their electrode potentials determined under specified conditions the order shows the tendency of one metal to reduce the ions of any other metal below it in the series. See also Electronegativities. 

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