averageaussie - 8-5-2023 at 18:09
Hello again all,
I believe I read somewhere that any element with a standard reduction potential below zinc's, -0.76 V, cannot be reduced out of an aqueous solution. I
was wondering why this was, and if it is correct in the first place.
Thanks, averageaussie.
clearly_not_atara - 8-5-2023 at 20:38
It's not really about zinc. It's about the reaction:
H2O + e- >> OH- + H2 (V = -0.8277)
with a standard electrode potential just below that of zinc. Below that, water is reduced instead. Zinc just barely slides in under the wire.
j_sum1 - 9-5-2023 at 03:04
Correct (apart from Bismuth) as CNA said. Because anything less than this will reduce water to H2 and hydroxide.
On the wikipedia page you can see the relevant line at -0.8277V in bold.
Another line in bold shows how O2 can be produced from water giving H+ ions (of course, it is listed in reverse as a reduction reaction at +1.229V).
Half reactions between these two in bold are all the possible reactions that can be done in aqueous solution. Outside those bounds and you crack your
water molecules preferentially.
https://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)
Note that that is at standard conditions of temperature and concentration. You can bend the rules a little with different concentrations. You can
also make some reactions occur by applying overpotential.