[JiminyCricket]

If metalic iron is placed in water with pH of 2 (sulfuric acid), will divalent or trivalent iron be favored?
What effect do hydronium ions have on an iron atom's valence electrons?
What is the equation to use for this calculation based on concentrations?

thanks

[Hunter2]

First you will get divalent iron, because its a reducing medium (Hydrogen development). In long term the oxygen from the air will oxidize to trivalent. The hydronium ions have no effect to iron valence electrons. The last question I don't understand, what do want to know exactly.

[AdiDex]

Fe is stronger reducing agent than Hydrogen so Fe will reduce it and get oxidize to Fe²⁺ .
After that reaction is as follow -:

2Fe²⁺ + SO₄^2- + 4H⁺    2Fe³⁺ + SO₂ + 2H₂O

It's all about Le chatelier's principle. If you are taking quite concentrated H₂SO₄ then you will get sufficient amount of Fe³⁺ .

Fe will donate electron to Hydronium Ion , To form H· and H₂O . Then H₂ gas will form .

[Hunter2]

I don't think your reaction will take place. Iron-II-sulfate is very stable also in acidic solutions. Oxidation only takes places with Oxygen or other oxidizers. Never seen that SO₂ will be developed. Concentrated acid is stored in stainless steel barrels and also pumped through metal pipes.

[Borek]

Thank you all for breaking forum rules in series. JiminyCricket asked a question without showing any effort, Hunter2 and AdiDex gave final answers without trying to guide the OP to the answer. Shame on all three of you.

[Hunter2]

Sometimes I have feeling words will be deposited on a gold balance here. Yes maybe the TES should do more by him/her self. And this is not a homework forum, I also know and have learned. But not everybody is a student. Sometimes somebody has a question and ask the "experts". Why not get an answer without more effort in advance. Life is sometimes not black and white. If you like you can erase the whole threat. You have the power as admin.

Have a nice day

[JiminyCricket]

I'm not a student. I'm working with Ferroplasma acidarmanus (fer1) in metal processing. I took gen chem in college and two semesters in organic. I have a master's in microbiology and work as a biotechnologist. Yes, I am asking the experts because I'm not one.

I understand pKa and how pH is calculated. I understand solubility rules. I understand redox reactions.

I'm looking for the equation for the prediction of the relative concentrations of the two iron ions (ferrous and ferric) in water at a certain pH.

I am trying to graph it out, but need an equation. pH vs concentration of ferrous iron.

Ferroplasma acidarmanus feeds off pyrite (FeS) I was wondering if it would feed off metallic iron in solution. Metallic iron rarely exists in nature.

The optimal pH of Ferroplasma is 1.7.

Enzymes in Ferroplasma oxidizes ferrous to ferric iron yielding ATP from ADP. It gets ferrous iron from pyrite deposits dissolved in acidic freshwater.

Borek, I am just looking for an equation. I know that ferrous iron is favored in acidic solution. Ferritin is a protein that binds to ferric iron in every cell in your body. Your blood pH is 7.4. You can't guide me to this solution. There's no intermediate step. I assume you moved my topic from inorganic chemistry to undergraduate chemistry. That action was in no way helpful or beneficial. The entire inorganic chemistry forum is full of solubility topics, including ones with iron.

I understand that Ferrous sulfate is stable in acidic solutions, Hunter2, the sulfuric acid is already in solution before the metallic iron is introduced. No reaction takes place besides the iron dissolving. The enzymes in Ferroplasma oxidize the ferrous iron with oxygen. Thanks though

AdiDex, I can't find a solubility constant for iron in acidic water. The concentration of acid in solution in my bioreactor may change, so the solubility constant may need to be a variable. Thanks

This journal article about Ferroplasma metabolism has a lot of inorganic chemistry that I'm unfamiliar with:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3305923/

I just need the equation for iron ions in solution.

Thanks

[Borek]

pH vs concentration of ferrous iron.

There is no such equation.

Note that you ask about an equilibrium between Fe(II)/Fe(III). That's a redox process. You can't tell what it yields not knowing what is the other half reaction. Hunter already explained what to expect in the solution qualitatively, for a quantitative treatment you need more data than you are supplying at the moment.

Google for iron Pourbaix diagram - it is the closest thing to what you are looking for. However, it uses additional information about the redox potential present in the solution. As long as you don't control it there is no way of telling what are the concentrations of ions present.