Frost diagrams oxygen

Figure 2.2. Frost diagram (i.e., AG°/F vs oxidation state) for the oxygen system in water.

FIGURE 8-5 Frost Diagrams for Oxygen, (a) Acidic solution, (b) Basic solution. 

From the Frost diagram in Figure 23.15, it can be seen that the most stable oxidation state of uranium in aqueous acid is U (i.e., it has the most negative free energy of formation, the quantity plotted on the y axis). However, the reduction potentials for the U02 /U02 and U02 /U couples are quite small, +0.170 and +0.38 V, respectively (hence, the U02 /U potential is +0.275 V). Therefore, b ause the O2/H2O reduction pwtential is 1.229 V, the most stable uranium ion is U02 if sufficient oxygen is present ... 

Figure 5.1 Modified Frost diagrams for (a) hydrogen, (b) oxygen and (c) carbon, illustrating different pathways for oxygen production from water oxidation, hydrogen evolution and CO2 reduction, at pH 7 versus a Normal Hydrogen Electrode (NHE) reference.

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