Nernst equation solubility constants

Application of the equilibrium constant equation along with the value for [Fe+ ] and then the Nernst equation containing values for E and E° and the concentration changes (0.10 M for all other soluble species) will give accurate pH values for comparison with the estimates from the diagram. The estimated values from the diagram are again presented in brackets. 

The half-reactions in (c), (e), and (f) are obtained by combining the solubility constant expressions in (d) and (g) with the basic Nernst expressions (a) and (b), equations (12-6) and (12-7). One example should make the method clear. Let us derive the e line. 

On the basis of the above considerations, Eq. (7.6) can be derived. It is a specific form of the Nernst equation with concentration values rather than activities. The constant E is a modified standard potential considering all effects of solubility equilibria ... 

Once we have determined the concentration of Ag+ ions from the Nernst equation for the cell, we can calculate the equilibrium constant by using the expression for the solubility product. 

The increase in apparent Km values observed following the immobilization of enzymes is also readily explained by considering local effects at the carrier surface. Recalling the Michaelis-Menten equation (v = Vmax[S]/ m+ [S] ), and its derivation (Chapter 2), we know that for soluble enzymes, Km is independent of enzyme concentration and is a constant under a given set of conditions. Immobilized enzymes suspended in an aqueous medium have an unstirred solvent layer surrounding them, called the Nernst or diffusion layer. Substrates and products must diffuse across this layer, and, as a result, a concentration gradient is established for both substrates and products, as shown in Figure 4.7. 

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