Question

23) Which of the following is the first, or initiator, reaction in acid mine drainage and leaching?

A) oxidation of reduced sulfides to sulfate and the release of reduced iron (Fe2+)
B) rapid spontaneous reduction of oxidized iron (Fe3+)
C) rapid oxidation of sulfides to sulfate by oxidized iron (Fe3+)
D) microbial sulfate reduction

Answer 1

The first reaction in acid mine drainage is the oxidation of reduced sulfides to sulfate and the release of reduced iron (Fe2+).

Step-by-step explanation:

The first, or initiator, reaction in acid mine drainage and leaching is the oxidation of reduced sulfides to sulfate and the release of reduced iron (Fe2+). This reaction can be represented by the equation:

Fe2+ (aq) + H₂S(g) + 2H₂O(l) → FeS(s) + 2H3O+ (aq)

In this reaction, the sulfur in hydrogen sulfide oxidizes to elemental sulfur, unless a large excess of the oxidizing agent is present, in which case the sulfide may oxidize to SO3²- or SO4²-.