Nemst expression

The reversible/equihbrium (as understood above) potential at a metallic electrode that is in equilibrium with its ions (no net reaction e.g., Ag, Ag+) is given by the well-known Nemst expression ... 

Since, however, it has been stipulated that the equilibrium situation is being considered, one can use the Nemst expression (7.51) for the equilibrium potentials and write101... 

When Eqs. (2.2) and (2.3) are combined, the resulting Nemst expression relates the half-cell potential to the effective concentrations of the redox couple ... 

Table 5.10 summarizes the presently available electrodes categorized as glass, ion-exchange membrane, crystal membrane, and liquid membrane. These electrodes can be used either for direct potentiometric measurements of ionic activity after calibration of the Nemst expression for the particular electrode or to monitor a potentiometric titration when a selected reaction that involves the monitored ion is available. Table 5.10 also indicates the common interfering ions. Several instrument companies are endeavoring to develop potentiometric-membrane electrodes to monitor directly ions in body fluids. 

Prior to the endpoint the Nemst expression of Eq. (4.2) is most convenient for computing the indicator potential. In contrast, past the equivalence point Eq. 

If the chronopotentiometric reaction involves a thermodynamically reversible process without complications, Eq. (4.17) may be used to relate concentrations to transition times in the Nemst expression. For a system where both reactant and product are soluble species (such as in Figure 4.11), the chronopotentio-gram is described by the relations... 

This activated platinum-electrode system is the equivalent of an NHE, and therefore conforms to the Nemst expression of Eq. (8.2). Rearrangement gives... 

Suppose, however, that the solution in the reaction vessel does not contain any ferrous ions. Then what is the concentration or activity that must be inserted in the Nemst expression for the equilibrium potential of the Fe2+ + 2e —- Fe reaction What value should be used for cPe2+ in... 

Third, consider a triangular cyclic potential sweep under reversible (Nerns-tian) conditions for a planar electrode (Fig. 6.10), to derive a cyclic voltam-mogram (Fig. 6.11) In the Nemst expression, Eq. (6.19.14) a time-dependent potential is added E(t) = E(0) — vt, whence... 

Typical half-cell reactions and their corresponding Nemst expressions follow. 

The Nemst expression in part (5) of Example 18-2 requires an excess of solid AgCl so that the solution is saturated with the compound at all times. 

The electrochemical potential of electrons in a redox electrolyte is given by the Nemst expression... 

When Tip,redox is moved down, that is more positive, the band bending increases, ysc increases and thus so decreases. A similar alteration in Cqx affects fp, redox through the Nemst expression. In both instances, we are influencing the Fermi level at the interface at equilibrium. Thus, in a sense, j o is a quantitative measure of the extent of rectification of a given interface that is, a smaller io value translates to better rectification. 

Again these equivalent equations can be used to develop a Nemst expression of the potential, that is Eq. (D.58) expressed as Eq. (D.59) in standard conditions of temperature and oxygen pressure (i.e., P02 of value unity) ... 

Comparing this with the Nemst expression we see that the solution pres P is... 

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