Question

The pathogenic bacterium Salmonella enterica uses tetrathionate found in the human gut as an oxidant- just as we use${\mathbf{O}}_{\mathbf{2}}$to metabolize our food. Write the half-reaction in which tetrathionate serves as an oxidant. Is tetrathionate as powerful an oxidant as${\mathbf{O}}_{\mathbf{2}}$?

Short answer

The half reaction of tetrathionate as an oxidant is,

${\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}+2\mathrm{e}\leftleftarrows 2{\mathrm{S}}_2{{\mathrm{O}}_3}^2$

Step-by-step solution

Definition of redox titration

• Redox reactions are oxidation-reduction chemical reactions in which the oxidation states of the reactants change. The term redox refers to the reduction-oxidation process.
• In a redox reaction, or Oxidation-Reduction process, the oxidation and reduction reactions always happen at the same time.

Determine the half reaction in which tetrathionate as an oxidant.

Half reaction of tetrathionate as an oxidant:

${\mathrm{S}}_4{{\mathrm{O}}_6}^{2-}+2\mathrm{e}\leftleftarrows 2{\mathrm{S}}_2{{\mathrm{O}}_3}^2{\mathrm{E}}^0=0.080\mathrm{V}$

Half reaction of oxygen as an oxidant:

$\frac{1}{2}{\mathrm{O}}_2+2{\mathrm{H}}^{+}2{\mathrm{e}}^{-}\leftleftarrows {\mathrm{H}}_2\mathrm{O}{\mathrm{E}}^0=1.23\mathrm{V}$

Values of standard reduction potential for each reaction can be found in appendix H. Since oxygen has a higher potential value it is a stronger oxidant than tetrathionate.