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Nemst s equation

Laplace transformation, 1215 Nemst s equation and. 1217 non-steady, 1254 as rate determining step, 1261 Schlieren method, 1235 semi-infinite linear, 1216, 1234, 1255 in solution and electrodeposition, 1335 spherical. 1216. 1239 time dependence of current under, 1224 Diffusion control, 1248... [Pg.33]

Nevertheless, the earlier thermodynamic treatment left one significant equation still very much present and effective when a change toward the kinetic approach occurred. This equation (Nemst s law) is used today and probably will be used even when all electrochemical calculations are wrapped up inside various companies software offerings. Nemst s equation,11 which treats the electrode/solution interface at equilibrium in a thermodynamic way, is the subject of the following section. [Pg.340]

This question is easy to answer There is always an equilibrium condition at the base of the discussion of any kinetic process. Nemst s equation is the electrochemical version of the well-known thermodynamic equation, AG = AG°+/KTln 0 /aKacam which forms a basic part of the treatment of equilibrium in chemical reactions and which is deduced and discussed in every thermodynamics text. Indeed, one can deduce Nemst s equation from it For at equilibrium ... [Pg.347]

The electrostatic aspects of electrochemical systems will be introduced first and the electrochemical potential as a key concept is presented (Sects. 1.2-1.4). The electrochemical equilibrium is discussed and Nemst s equation and standard and formal electrode potentials are introduced (Sect. 1.5). The study of electrochemical interfaces under equilibrium ends with the phenomenological and theoretical treatment of the electrical double layer (Sect. 1.6). [Pg.2]

If the activities of species O and R are different from the unity, the Nemst s equation is obtained,... [Pg.13]

When other reference electrodes are used as, for example, the saturated Calomel electrode (SCE), a constant quantity needs to be added to the right-hand side of Nemst s equation which reflects the difference between the SCE and the SHE electrodes, i.e., in this case the standard potential is... [Pg.14]

It is very rare for the activities of all species involved in an electrode reaction to be constrained to be the unity. In general, the electrode potential is influenced by these activities in the form given by the Nemst s equation (Eq. 1.36). When the reactants or products are in solution, the Nemst s equation can be approximated by replacing the activities by the concentrations, but this can be a very rough approximation in the case of ions. The usual procedure, given that the activity coefficients are almost always unknown, is to incorporate them into the E ° term writing, for example... [Pg.14]

An electrochemical reaction is called reversible or nemstian when the Nemst s equation can be applied to the surface concentrations of electroactive species for any value of the applied potential (see Sect. 1.7). [Pg.69]

The obvious value to insert for cFe21 is zero in which case Nemst s equation for the electrode potential of the Fe2+ + 2e Fe equilibrium indicates a value that would be highly negative. Since this potential is negative with respect to the equilibrium potential of any possible electronation reaction, the iron will start dissolving and building Fe2+ concentration in the solution layer that is in contact with the electron-sink area of the iron. If this layer is stagnant and the Fe2+ ions are not removed by a chemical reaction, e.g., precipitation, the Fe2+ concentration will climb up from zero. Clearly, the Fe2+ ion concentration adjacent to the metal is determined by the amount of metal that has dissolved, and how fast this diffuses away. [Pg.136]

The decrease of the decomposition voltage is at first sight difficult to comprehend and it cannot be explained by Nemst s equation, according to which the equilibrium deposition potentials of hydrogen and oxygen increase with increased pressure. The equation (X—8) expresses the relation between the reversible water decomposition potential and the gas pressure at 25 °C ... [Pg.228]

Herzi3 found that in Nemst s equation (2) MlJTb=9-5 og r —O-OO =f(rfi), the value of f(r ) is usually larger than MlJTb and increases with the... [Pg.364]

The measured potential E is described by Nemst s equation as follows ... [Pg.61]

The one-electron reduction potential of interest is then calculated from the equilibrium constant and the one-electron reduction potential of the redox reference couple using Nemst s equation (AE° = 0.0591 log K). While electrochemical techniques often yield irreversible oxidation potentials, pulse radiolysis usually yields thermodynamically correct one-electron reduction potenticils, provided the reactions are fast... [Pg.323]

Strategy The standard emf (E°) can be calculated using the standard reduction potentials in Table 19.1 of the text. Because the reactions are not run under standard-state conditions (concentrations are not 1M), we need Nemst s equation [Equation (19.8) of the text] to calculate the emf ( ) of a hypothetical galvanic cell. Remember that solids do not appear in the reaction quotient (Q) term in the Nemst equation. We can calculate AG from E using Equation (19.2) of the text AG = -nFEcsW. [Pg.573]

When we are dealing with corrosion we can usually replace the activities in Equation (3.9) with concentration, partial pressure etc., as mentioned on page no. 18. Equation (3.9) is well known as Nemst s equation, after Walther Nemst, a German physicist and chemist (1864-1941). [Pg.23]

The Pourbaix diagram is a graphical representation of Nemst s equation for the various reactions. From the potential equations of the reactions a)-f) we obtain the Pourbaix diagram for iron in water at 25°C, as shown in Figure 3.10. Here, an activity of ferrous ions, a 2+> l is presumed. This order of magnitude is... [Pg.26]

The larger the activity of, e.g. in the solution, the more zinc ions are discharged. To balance this with a higher rate of ion release from the metal, a higher positive pressure is needed in the metal. That is, the equilibrium potential increases with increasing activity of metal ions in the liquid, in agreement with Nemst s equation ... [Pg.31]

As described in Chapter 3, and expressed by Nemst s equation (3.9), the equilibrium potential depends on the activity, or practically on the concentration of the species that take part in the reaction. The reduction of the oxygen eoneentration that oeeurs close to the metal surface when the electrode is polarized in the eathodie direetion, leading to the concentration profile shown in Figure 4.4, causes therefore a change in the equilibrium potential. This equilibrium potential shift is regarded as an overvoltage ... [Pg.42]

The complete determination of position and shape of overvoltage curves requires knowledge about the quantities io, it, be, and ba, of which the first one is given by Nemst s equation or the Pourbaix diagram. Through such knowledge, the best tool we have for description of the kinetics of electrode reactions is available. With a reservation for passivation effects (which we shall return to) we can with this background obtain a quantitative description of any corrosion process, in principle as shown in Section 4.9. [Pg.44]

When there is an oxidizer in the liquid and the concentration of this is increased, the corrosion potential is generally increased, as shown in Figures 6.1 and 6.2. The shift is due to the activity term in the reversible potential equation (Nemst s equation, (3.9)) increased activity of oxidizers gives increased reversible potential for the cathodic reaction. This may lead to an increase in corrosion rate, as shown on the right in Figures 6.1 and 6.2 for active and active-passive metals, respectively. [Pg.65]

Write down the reaction equation for reduetion of O2 as well as Nemst s equation in eaeh of the two cases. Explain the similarity and the difference between eorresponding addends in the Nemst s equation in the two cases. Indieate the standard equilibrium potential of the reactions and the equilibrium potential as a function of the pH at p02 = 1 in a pH-potential diagram. [Pg.86]

If we allow for the concentration dependency of the chemical potential in relation (22.19), we obtain another version of Nemst s equation. Thus, according to Eq. (22.18), the following is valid for the electron potential of the redox pair in the solution ... [Pg.535]

As we would expect from relation (23.2), the redox potential shows the same concentration dependency as the Galvani potential difference [Eq. (22.23)]. The various versions of Nemst s equation generally exhibit great similarity to the proton level equation [Eq. (7.12)]. This equation describes the dependency of proton potential upon the ratio of acid and base concentrations, i.e., upon c(Ad)/c(Bs). The similarity results from the direct relation of the Galvani potential difference of a half-cell or its redox potential with the electron potential fie [Eqs. (22.19) or (23.3)], which is formally closely related to the proton potential. [Pg.554]


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See also in sourсe #XX -- [ Pg.61 ]

See also in sourсe #XX -- [ Pg.23 ]

See also in sourсe #XX -- [ Pg.530 , Pg.536 , Pg.554 , Pg.564 ]

See also in sourсe #XX -- [ Pg.9 ]




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Equation Nemst

Nemst

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