Manganese potential diagram

Thermodynamic data (4) for selected manganese compounds is given ia Table 3 standard electrode potentials are given ia Table 4. A pH—potential diagram for aqueous manganese compounds at 25°C is shown ia Figure 1 (9). 

A Latimer diagram shows the standard electrode potentials associated with the different oxidation states of an element, as illustrated in Fig. 1 for manganese. Potentials not given explicitly can be calculated using Equation 1 and taking careful account of the number of electrons involved. Thus the... 

Fig. 7.2 Potential diagrams (Latimer diagrams) for manganese in aqueous solution at pH 0 (i.e. [H j = 1 mol dm ), and in aqueous solution at pH 14. For such diagrams, it is essential to specify the pH, and the reason is obvious from comparing the two diagrams.

Fig. 22.12 Potential diagrams for technetium and rhenium in aqueous solution at pH 0 compare with the diagram for manganese in Figure 7.2.

Frost Ebsworth diagram for manganese in aqueous solution with [H ] = 1 moldm . This diagram can be constructed from the corresponding potential diagram in Figure 8.2 as follows. 

The electrode potential diagram for manganese in acidic solutions in Figure 23-14 does not include a value of " for the reduction of Mn04 to Mn. Use other data in the figure to establish this E°, and compare your result with the value foimd in Table 19.1. 

Example 2.12 In the Latimer diagram for manganese in acidic medium, (a) find the values of E and Eg (see the table below), (b) draw the Frost diagram, and (c) find which is the most stable species of this system in acidic aqueous solution. The standard potential data are summarized in the table given above. 

Figure 5 Redox predominance diagrams for iron (a) and manganese (b) boundaries represent the standard reduction potential for reduction of the (thermodynamically-stable) species above the boundary to the (thermodynamically-stable) species below the boundary. If the redox predominance regions of two species (e.g., the gray regions of Fe + and Mn04 ) do not overlap along the y-axis when the two diagrams are superimposed, reaction between the two species is thermodynamically favored...

FIGURE 21.25 Potential-pH equilibrium diagram for the manganese-water system at 25 °C. [Considering Mn02 (pyrolusite).] (from Ref. 37). 

Fig. 14.2 A potential-pH (Pourbaix) diagram for manganese. IModified from C. C. Liang In Encyclopedia of Electrochemistry of the Elements Bard,...

Within the area of interest in the stability diagrams, ferric hydroxide precipitation is possible at lower oxidation potentials than manganic manganese oxides at any given pH. Similarly, at a fixed Eh ferric hydrox-... 

The redox potential-pH stability diagram (Figure 12.11) indicates that between pH 7 and 8, zinc carbonate (ZnCOj) is formed when the concentration of dissolved carbon dioxide (CO2) is 10 mol L . At low redox values, zinc sulfide is the most stable combination. Zinc precipitation by the hydrous metal oxides of manganese and iron is the principal control mechanism for zinc in wetland soils and freshwater sediments. The occurrence of these oxides as coatings on clay and silt enhances their chemical activity in excess of their total concentration. The uptake and release of the metals is governed by the concentration of other heavy metals, pH, organic and inorganic compounds, clays, and carbonates. 

Figure 8 The predominance diagram (Pourbaix diagram) indicating the pH-redox potential interaction for manganese species in aqueous solution. The dotted lines indicate the thermodynamic water stability region. The full lines correspond to 1 mol I concentration of species in the liquid phase, the dashed lines to 10 molconcentration.

Figure F.13 Potential-pH equilibrium diagram for the manganese-water system at 25°C.

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