Aqueous solution chemistry of sulfur, selenium and tellurium

   As we saw earlier in the chapter, the redox reactions between compounds of S in different oxidation states are often slow, and values of Eo for half-reactions are invariably obtained from thermochemical information or estimated on the basis of observed chemistry. The data in Figure 1.1 illustrate the relative redox properties of some S-, Se- and Te-containing species. Points to note are:

• the greater oxidizing powers of selenate and tellurate than of sulfate;

Fig. 1.1 Potential diagrams for sulfur, selenium and tellurium at pH = 0.

• the similarities between the oxidizing powers of sulfate, selenite and tellurite;
• the instabilities in aqueous solution of H₂Se and H₂Te.