Nemst effect

Zik, thermoelectric T.m, Nemst effect Zikim, magneto- second-order... 

Nemst effect - The production of an electric field in a conductor subject to an applied magnetic field and containing a transverse temperature gradient. The electric field is perpendicular to the magnetic field and the temperature gradient. 

Checkelsky JG, Ong NR. Thermopower and Nemst effect in graphene in a magnetic field. Rhys Rev B Conden Matter Mater Rhys 2009 80 0814131-4. 

The laboratory temperature during titration is rarely equal to the ambient temperature or process temperature. The sample pH will change with temperature since the dissociation constants and water ionic product change with temperature. This is a change in actual solution pH and is not to be confused with the change in millivolts generated by the glass electrode per the Nemst Equation in Chapter 4. Conventional temperature compensators use a temperature sensor embedded inside the electrode to correct for the Nemst effect. 

The decrease in voltage is due to three different contributions, linked to the concentration of the reactant on the anode side the Nemst effect, the charge transfer on the anode electrode mass transport on the anode channel and on the electrode. 

Gibbs values and the effective electrode potential follows the Nemst equation (see section C2.11). For the oxidation (anodic) reaction, the potential (E ) of the Nemst equation can be written as ... 

These three terms represent contributions to the flux from migration, diffusion, and convection, respectively. The bulk fluid velocity is determined from the equations of motion. Equation 25, with the convection term neglected, is frequently referred to as the Nemst-Planck equation. In systems containing charged species, ions experience a force from the electric field. This effect is called migration. The charge number of the ion is Eis Faraday s constant, is the ionic mobiUty, and O is the electric potential. The ionic mobiUty and the diffusion coefficient are related ... 

The EMD studies are performed without any external electric field. The applicability of the EMD results to useful situations is based on the validity of the Nemst-Planck equation, Eq. (10). From Eq. (10), the current can be computed from the diffusion coefficient obtained from EMD simulations. It is well known that Eq. (10) is valid only for a dilute concentration of ions, in the absence of significant ion-ion interactions, and a macroscopic theory can apply. Intuitively, the Nemst-Planck theory can be expected to fail when there is a significant confinement effect or ion-wall interaction and at high electric... 

Since the separation between the tip and the surface is such that their respective double layers do not overlap, the nanostmcturing process can be described simply through the diffusion of the ions toward the surface. Thus, the concentration profiles of the diffusing ions dehne effective Nemst potential prohles that can be employed to predict the regions where the oversaturation conditions will contribute to metal nucleation and growth. 

Nemst, for example, argued that physics forms the theoretical basis of all sciences, including chemistry. 18 A statement by Emile Dubois-Reymond to the effect that there was a need for a physical chemistry to create a "mathematical mechanics of knowledge" and a "complete picture of molecular processes" 19 was used to preface the first issue of the Zeitschrift fur physikalische Chemie. For van t Hoff, this was to be achieved through "the application of physical expedients, methods, and instruments to chemical problems" in establishing "comprehensive principles."20 Less concretely, Jean Perrin wrote that "really, there is no particular method proper to chemical physics [but] rather a physicochemical esprit."21 Perrin s successors at the Universite de Paris understood this remark to mean that physical chemistry at the turn of the century was "whatever interested Jean Perrin, just as physical chemistry at Berkeley was whatever interested Gilbert N. Lewis. "22... 

For a triphasic reaction to work, reactants from a solid phase and two immiscible liquid phases must come together. The rates of reactions conducted under triphasic conditions are therefore very sensitive to mass transport effects. Fast mixing reduces the thickness of the thin, slow moving liquid layer at the surface of the solid (known as the quiet film or Nemst layer), so there is little difference in the concentration between the bulk liquid and the catalyst surface. When the intrinsic reaction rate is so high (or diffusion so slow) that the reaction is mass transport limited, the reaction will occur only at the catalyst surface, and the rate of diffusion into the polymeric matrix becomes irrelevant. Figure 5.17 shows schematic representations of the effect of mixing on the substrate concentration. 

Neopentyl alcohol (continued) effect of pyridine, 35 344 effect of sodium, 35 342 effect of temperature, 35 339, 341 mechanism, 35 347 over nickel-kieselguhr, 35 348 Nemst s law, 40 117 Neutral ligands... 

When will the effect of the mean ionic activity coefficients be most likely to affect the accuracy of the concentrations calculated by the Nemst equation (Hint - when is the value of activity most like the concentration )... 

We will now look at the effects of Ej on thermodynamic calculations, and then decide on the various methods that can be used to minimize them. One of the most common reasons for performing a calculation with an electrochemical cell is to determine the concentration or activity of an ion. In order to carry out such a calculation, we would first construct a cell, and then, knowing the potential of the reference electrode, we would determine the half-cell potential, i.e. the electrode potential E of interest, and then apply the Nemst equation. 

The plots shown in Figure 6.3 show the variations of the concentrations of both reduced and oxidized forms ofTl (of reactant Tt in Figure 6.3(a) and product Tl in Figure 6.3(b)). Each concentration is depicted as a function of the distance from the electrode solution interface where oxidation is effected these curved traces are often termed concentration profiles. Each of the figures incorporate a series of concentration profiles, drawn as a function of time, to show how the Nemst layer increases in thickness during electrolysis, because the extent of electromodification has increased with time. 

Activity a and concentration c are only the same at extremely small concentrations (y = 1 if c < 10 mol dm ), so in such cases the values of E will be the same whichever variable is inserted into the Nemst equation. Conversely, as the concentration rises, so y decreases. We see then that c a, so the effects of y are seen most prominently at higher concentrations. 

The diffusion flux J, in mol/cm, is proportional to the concentration gradient and inversely proportional to the diffusion layer s effective thickness 5 (also called the Nemst thickness). The proportionality constant D is the diffusion constant hence,... 

C) The question concerns the effect of changing standard conditions of a cell to nonstandard conditions. To calculate the voltage of a cell under nonstandard conditions, use the Nemst equation... 

For inter diffusion between same-valence ions (ionic exchange) in an aqueous solution, or a melt, or a solid solution such as olivine (Fe +, Mg +)2Si04, an equation similar to Equation 3-135c has been derived from the Nemst-Planck equations first by Helfferich and Plesset (1958) and then with refinement by Barter et al. (1963) with the assumption that (i) the matrix (or solvent) concentration does not vary and (ii) cross-coefficient Lab (phenomenological coefficient in Equation 3-96a) is negligible, which is similar to the activity-based effective binary diffusion treatment. The equation takes the following form ... 

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