PH-charge diagram

Fig. 7.5. Charge-pH diagram giving the existing domains in aqueous media for substituted ionic...

Figure 1 Charge/pH diagram indicating the domains of aquo, hydroxo, and oxo species (reproduced by permission from Inorganic Complexes Academic Press London, 1963).

The partial-charge model can be used to calculate the magnitude of charge transfer between oxo, hydroxo, or aquo ligands and allowing calculation of the charge-pH diagram (Fig. 1). Under acidic conditions, spontaneous hydrolysis ... 

Hydroxylation of the metal cation may be obtained through an acid-base reaction (neutralization, thermolysis, etc.) or through an oxidation-reduction reaction. The charge-pH diagram (Figure 1.6) shows that reduction and oxidation of cations as 0x0 and aquo species, respectively, allows them to reach the stability domain of hydroxo forms. Hydroxylation is the initiation stage of the process and the hydro-xylated complex is the precursor of the condensation products. 

Oxolation is the process of creation of oxo bridges between cations that do not have aquo ligands in their coordination sphere [1]. Therefore, this reaction occurs only with elements of high formal charge (z 4), which exist in a dilute alkaline or neutral medium as oxo anions or oxo-hydroxo monomers [Si(lV), Cr(VI)] (see Section 1.1, charge-pH diagram). 

In their maximum oxidation state, V(V), Cr(VI), Mo(VI), W(VI) and Mn(Vll) have the d electron configuration, carry a high charge and are relatively small. In an alkaline medium, they exist as tetraoxo [M04] monomers [2] (see Section I.l, charge-pH diagram). 

Oxidation kinetics, 292-293 Reduction kinetics, 288 Removal from solution, 443-445 pe-pH diagram, 256,441 Manganese carbonate, 59,433 Manganese oxides, 131 Methane, 257-258, 324 Mica, 102-108 Layer charge, 113 Structure, 115 Molecular Weight, 13,14 Mole fraction, 202 Equivalent fraction, 202 Montmorillonite., 102,104, 109, 123 C-axis spacings, 171 Layer charge, 120 Structure, 171 Composition, 104 Physical properties, 123-124 Chemical properties, 123-124 Muscovite, 104, 123 Structure, 108 Composition, 104... 

FIGURE 8.14 Charge vs. pH diagram indicating the aquo, hydroxo, and oxo domains for the hydrolyzed cations. The possible initiation mechanisms for condensation reactions are indicated. (From Jolivet, J.-P., Metal Oxide Chemistry and Synthesis, John Wiley Sons, Chichester, U.K., 2000, 34. With permission.)... 

The remaining equation necessary to describe the system is either the proton condition or the charge balance. Since these equations are based on concentration rather than activity, no correction for ionic strength is necessary. The pC-pH diagram in Fig. 4-4 can now be used to obtain concentrations as previously demonstrated. 

We use equations (1), (3), and (4) to plot a pC-pH diagram for the acetic acid-acetate system (Ct,ac = 10 M) (Fig. 4-12). To determine the solution pH after each NaOH addition, we must first determine Na from equation (2) and then substitute this value in the charge balance, equation (5). The solution for the charge balance is obtained by inspection of the pC-pH diagram. For V 0.0025 liter From (2)... 

To determine the solution composition, we need the mass balance, the charge balance, and the appropriate pC-pH diagram. 

These equations can be rearranged so that the concentration of each complex is expressed as an equilibrium with solid Al(OH)3(s as was done for Fe(OH)3(s). The pC-pH diagram plotted from these equations (Fig. 6-8a) shows that the large, highly charged polymeric species such as Ali3(OH)34 + and Al7(OH)i7 + control Al(OH)3(s) solubility below a pH value of approximately 6.5. 

The potential/pH diagram shows that, at low pH values, the equilibrium potential of the H /H2 electrode has more positive values than that of the Pb/PbS04 electrode. It should be expected that H2 will evolve first during battery charge. However, because of the high over-potential of hydrogen evolution on Pb, the above process does not proceed. Instead, PbS04 is reduced... 

Fig. 43. Position of the reversal of charge in a mixing proportion — pH diagram (according to the data of Fig. 42).

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