Can Fe2+ ions exist in an acidic solution or will they always pick up available protons and become Fe3+? My hunch is they can't exist but I'm not really sure.
If the latter, does that mean that dissolving iron in an acid will raise the pH since it ties up some of the H+? Or will the additional protons still be just as free to float around and interact with other stuff as they are before iron comes to the party?
If they can exist, however, is there some kind of ferric:ferrous equilibrium based on... something?
I ask because I have a solution of oxalic acid and water, with iron dissolved in it, and it is bright yellow-green (like a green or yellow highlighter), and the internet says Fe3+ ions are yellow-green. Also I'm pretty sure there can't be actual iron oxalate particles (which are also green) suspended in the solution (conclusion from this lesson). I'm trying to work out the actual contents of the solution on my own.
So I'm pretty sure I'm looking at ferrIC ions -- and it doesn't seem to make sense that ferrous ions could exist here -- but I just want a sanity check on that guess, since I'm still trying to wrap my head around this.
As an aside: Now after a little more reading, I'm wondering if maybe my oxalic acid solution contains ferrioxalate ions too (or instead), although that's specific to my oxalic acid experiments rather than acids in general. They're also bright green, it seems. Apparently those are light sensitive though, so maybe my UV laser will do something if the wavelength (405nm) is right and so I can test for them? That's an experiment for tomorrow.