averageaussie
Hazard to Self
![*](images/xpblue/star.gif)
Posts: 64
Registered: 30-4-2023
Location: Right behind you
Member Is Offline
Mood: school
|
|
reduction potential
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
International Hazard
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 2731
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
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
Administrator
![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif) ![*](images/xpblue/star.gif)
Posts: 6269
Registered: 4-10-2014
Location: Unmoved
Member Is Offline
Mood: Organised
|
|
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.
|
|