Hey guys,
I just had a doubt about electrolysis. Let’s say there’s a half cell that has Fe at it’s anode and an inert carbon cathode and an aqueous electrolyte ( AgCl ). Fe is the strongest reductant and will therefore get oxidised. However, since Ag ions are the strongest oxidant than Fe ions, wouldn’t it undergo reduction and the cathode be electroplated with Ag?
Hey! I'm not too sure about what you're confused about but everything that you've stated seems to be consistent and doesn't seem to be contradictory or confusing.
Your statement about Fe being the strongest reductant is technically correct but with electrolysis, it doesn't matter which one is the strongest reductant because you are
choosing which species oxidises by connecting it to the positive terminal of a battery. Therefore, by choice, we are forcing the oxidation of Fe to Fe
2+ ions (this is why Cl
- doesn't oxidise to Cl
2) and note that we can really use whatever cathode we like because in electrolytic cells, the cathode effectively remains inert. What we don't get to choose with electrolysis however is which species reduces (oxidant). By oxidising Fe to form Fe
2+ ions, the possible oxidants in the cell are Fe
2+, Ag
+ and H
2O (as we have an aqueous species). Assuming that conditions are at SLC, Ag
+ is the strongest oxidant and therefore will reduce preferentially on the graphite cathode.
Hope this clears things up!