<p>How much pyrite has to be oxidized to produce a sulfate concentration of 15 mM? </p>

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

CC BY-SA 3.0
2018-01-13T04:20:07.787Z
Do you know what is the oxidation reaction of pyrite?
Gimelist
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2018-01-13T04:26:01.217Z
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
chrisuw92
CC BY-SA 3.0
2018-01-13T11:17:26.450Z
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.
Gimelist
CC BY-SA 3.0
2018-01-22T20:10:27.127Z
Please see the guide on how to ask homework questions: https://earthscience.meta.stackexchange.com/a/317/39
Semidiurnal Simon
<geochemistry><minerals><homework><groundwater>
Pyrite oxidation
chrisuw92
# Pyrite oxidation

(Asked by: username_0 on 2018-01-12)

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?

**Tags:** geochemistry, minerals, homework, groundwater

> **Comments:**
> **username_1**: Do you know what is the oxidation reaction of pyrite?  
> **username_0**: 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  
> **username_1**: 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.  
> **username_2**: Please see the guide on how to ask homework questions: https://earthscience.meta.stackexchange.com/a/317/39  

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