Nernst equilibrium potential

Passivation — Metals usually dissolve in acidic electrolytes when their electrode potential becomes more positive than the value of the related -> Nernst equilibrium potential of the metal/metal ion electrode. The dissolution current density increases exponentially with... 

Express the equilibrium potential in terms of ion conductances for a membrane permeable to both Na+ and K+ ions with relative conductivities gNa and gK- [Hint assume that the flux of each ion is proportional to conductivity multiplied by the driving force, which can be expressed as the difference between the membrane potential and the Nernst equilibrium potential for a given ion.]... 

Synthetic OHB19/23/polyP complexes demonstrated weak but explicit selectivity for divalent over monovalent ions79 when incorporated in planar bilayers composed of synthetic di22 l PC, cholesterol (5 1 w/w) between unequal solutions of Ca2+ and Na+ at pH 7.4 (Figure 15C). The reversal potential was -20 mV the Nernst equilibrium potentials were the same as for the synthetic complexes above. The data indicate selectivity for Ca2+ over Na+ of about 4 1, a significant improvement over channels formed by the oligomers alone (see Figure 8C), but still much poorer discrimination than the >90 1 selectivity demonstrated by the natural and synthetic... 

An increase in the permeability of the PM to sodium ions (Na+) permits Na+ to enter the cell down a concentration gradient with a consequent increase in the positive charge within the cell that opposes Na+ entry. At equilibrium there is no further net entry and v m approximates to the Nernst equilibrium potential (t]txj for Na+ given by the following equation (noting that. c =tlie charge on the ion (+1)) ... 

Similarly, increasing the permeability of the membrane to K+ (PK+) will permit K+ to flow out of the cell down a concentration gradient, this efflux of positively charged K+ causing the inside of the cell to be more negative with respect to the outside and hence increasingly opposing further efflux. At equilibrium, when there is no further net efflux of K+, the v]tm approximates to the Nernst equilibrium potential (vjt -) for K+ ... 

In this case, the Nernst equilibrium potential, jvie/Me + represents the limit of the stability ranges of both 2D and 3D Me phases. At " =, 2D and 3D Me... 

The corrosion behavior of metals cannot be predicted from the position of their standard potentials in the electrochemical series because the potential of an electrode changes with the current density. If an electrode in which only one electrode process takes place is termed a working electrode and the resultant potential, a working potential, then the differences between working potential and the Nernst equilibrium potential is called an overpotential, that is caused by reaction restraints. In general, polarization is defined as the shift in potential of working electrodes within a corrosion element. In such an element, at least two electrode reactions occur whose overpotentials are superimposed, resulting in the polarization effect. 

Sodium currents were evoked by voltage pulses from a holding potential of —90 mV to a membrane potential, of —60 to +80 mV for 3 ms (Fig. lOA). All stimulation for sodium currents was followed by a similar pulse protocol in which the pulse amplitude was reduced to 1/4 and the holding potential was brought to —120 mV (P/4 protocol [42]). A plot of the peak current as a function of the membrane potential is shown in Fig. lOB. The peak current was estimated by a cubic fit of each record in a short interval around the peak with a third-order polynomial. The reversal potential, V, i.e., the applied voltage for which the peak current changes sign is estimated around 53 mV, which is very close to the Nernst equilibrium potential for sodium ions in these experimental conditions. 

Following the seminal paper of Butler (37) in 1924 on the kinetic basis of Nernst equilibrium potentials, an electrochemical rate equation was written by Erdey-Gruz and Volmer (14), for a net current-density i, in terms of components of i for the forward and backward directions of the process. They recognized that only some fraction (denoted by a or 3) of the electrical energy change riF associated with change of electrode potential, would exponentially modify the current, giving a potential-dependent rate-equation of the form ... 

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