How is sulfuric acid produced in mine drainage? Write the correspondingstoichiometric equations

Sulfuric acid is produced in mine drainage through a series of chemical reactions involving pyrite (FeS2), a common mineral found in rocks. The process is often accelerated by the activity of certain bacteria, such as Acidithiobacillus ferrooxidans.

Here are the steps:

1. Pyrite reacts with water and oxygen to form ferrous iron and sulfate. The chemical equation for this reaction is:

   4FeS2(s) + 15O2(g) + 14H2O(l) → 4Fe2+(aq) + 8SO42-(aq) + 16H+(aq)

2. The ferrous iron produced in the first step can be further oxidized to ferric iron by bacteria:

   4Fe2+(aq) + O2(g) + 4H+(aq) → 4Fe3+(aq) + 2H2O(l)

3. The ferric iron can then react with more pyrite to produce additional ferrous iron, sulfate, and acidity:

   FeS2(s) + 14Fe3+(aq) + 8H2O(l) → 15Fe2+(aq) + 2SO42-(aq) + 16H+(aq)

These reactions result in the production of sulfuric acid (H2SO4), which is responsible for the acidity of mine drainage. The overall reaction can be written as:

2FeS2(s) + 7O2(g) + 2H2O(l) → 2Fe2+(aq) + 4SO42-(aq) + 4H+(aq)

The H+ ions combine with water to form H3O+ ions, which are responsible for the acidity of the solution:

H+(aq) + H2O(l) → H3O+(aq)

This is a simplified explanation and the actual process can be more complex, involving a variety of other reactions and species.