Redox as pe and the Standard Hydrogen Electrode SHE

TABLE 5.2. Reduction Potentials of Selected Half-Cell Reactions in Soil-Water Systems at 25°C 

Source Reproduced from Stumm and Morgan (1981) and Sparks (1995). 

TABLE 5.3. Electrode Potentials of Phenol, Acetic Acid, Ethanol, and Glucose 

TABLE 5.4. Equilibrium Constants of Redox Processes Pertinent in Soil-Systems (25°C) -Water 

Equation 5.23 demonstrates that as long as Fe3+ and Fe2+ are present in the system at equal activities, pe is fixed at 13.03. If electrons are added to the system, Fe3+ will become Fe2+, and if electrons are removed from the system, Fe2+ will become Fe3+. Equation 5.22 can be generalized for any redox reaction at 25°C, 

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