Several genera of sulfate reducing bacteria are abundant in anoxic (without O 2

Question

Several genera of sulfate reducing bacteria are abundant in anoxic (without O2), aquatic habitats and water-logged soils in which sulfate is abundant. They consume hydrogen gas (H2) as a food (electron) source, and rather than use O2 as an electron acceptor they use sulfate (SO42-). The byproduct of this reaction is the sulfide anion, which reacts with water to yield hydrogen sulfide gas (H2S), giving swamps and other stagnant bodies of water their lovely aroma.

The redox couples for this process are

SO42- + 8e- + 10 H+ « H2S + 4H2O                     Eo’ = -0.22 V

2H+ + 2e- « H2                                                         Eo’ = -0.42 V

a)   Write a balanced equation for the oxidation of H2 by SO42-

b)   What is the DeltaG°’ for the oxidation of H2 by 1 mole of SO42-?

Explanation / Answer

1. H2S + 4H2O + H2 = SO42- + 10H + 2H

2.G = -nF (E’0) n, the number of e– transferred.

= - (10 ) * 23 * + 0.64

= -147.2 Kcals/Mol

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