How much pyrite has to be oxidized to produce a sulfate concentration of 15 mM?

If the solution initially has a pH of 8, roughly what would the pH drop to if there is no buffering of acidity?

  • $\begingroup$ Do you know what is the oxidation reaction of pyrite? $\endgroup$
    – Gimelist
    Jan 13 '18 at 4:20
  • $\begingroup$ FeS2(s) + 15/4 O2(aq) + 7/2 H2O → Fe(OH)3(s) + 4H+(aq) + 2SO42-(aq) so I guess 7.5 mmol of pyrite is needed to produce 15 mmol of sulfate $\endgroup$
    – chrisuw92
    Jan 13 '18 at 4:26
  • $\begingroup$ Good. Now, if for each mol of pyrite you're generating 4 protons, what would be the effect on pH? Also notice that the question has mM - this implies a volume. If there is no other information, I reckon assuming 1 litre is safe. $\endgroup$
    – Gimelist
    Jan 13 '18 at 11:17
  • $\begingroup$ Please see the guide on how to ask homework questions: earthscience.meta.stackexchange.com/a/317/39 $\endgroup$ Jan 22 '18 at 20:10

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