I while back I made some iron(ii) chloride by reacting HCl with steel wool. This inevitably formed iron(iii) chloride. So I ended up with some nice flakes of yellow iron(iii) chloride in a (non airtight) container. However today I went back to the container to find that it had all turned dark brown. Why would this happen? It is as if it has oxidized, but I'm pretty sure Chlorine is more reactive than Oxygen which would surely mean there would be no displacement reaction occurring. Thanks in advance for any ideas/answers, Finkployd4658
It hydrolyses, see Wiki article: http://en.wikipedia.org/wiki/Iron(III)_chloride The Fe³⁺ ion abstracts OH⁻ from moisture, giving you an iron hydroxide complex and an acidic solution, effectively dilute HCl. Iron hydroxide is brown. The Cl⁻ anion is unaffected in this process, so the reactivity of chlorine does not come into it, as it happens.
Ahh thanks very much. So, seeing as the contents of the container seem quite dry, would it contain actual crystals of Hydrogen Chloride as well as of Iron Hydroxide? I don't know what color HCl crystals are but I have noticed there are small light blue crystals that have formed on the inside of the lid of the container (btw the container is metal, although I'm not sure exactly which metal)
Pure HCl is a gas at NTP so it won't form crystals. I suppose the blue may be a chloride of whatever the coating of the metal container is. Interesting you say it is dry, but I suspect atmospheric moisture, even if it is not much, will lie behind what has happened.
Ah right ok. Yeah, when I say its dry, I don't necessarily mean absolute devoid of any H2O. To be honest I wasn't very inclined to touch it that much Please Register or Log in to view the hidden image! Thanks again.
