Sciencemadness Discussion Board

Magnesium can reduce zinc ions to zinc metal?

ChemTalk - 14-2-2021 at 17:25

For some reason, I had thought that zinc was too reactive to be displaced in aqueous solution by a more reactive metal, and that reduction of hydrogen would be preferred.

But when I put magnesium ribbon in a zinc sulfate solution, it made elemental zinc - and it looks quite beautiful imho, looking like little shrubs.

I looked online pretty extensively, and I could not find any mention of anyone doing this before.

So I thought, either it was A) just not interesting enough for people to talk about, or B) maybe it is very difficult to do and I got lucky, or C) most people just don't try it, or D) did I just not look hard enough online?

Anyways, I continue to find chemistry amazing, even in the simplest experiments, like many of you.

Thanks for your comments in advance!

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ChemTalk
chemistrytalk.org


[Edited on 2-15-2021 by ChemTalk]

clearly_not_atara - 14-2-2021 at 17:33

It's concentration. In an aqueous solution of zinc sulfate (and nothing else), the concentration of [Zn2+] is probably about ten thousand times that of [H+]. Magnesium reacts very slowly with neutral water, and just barely in weak acids. Only strong acids produce rapid bubbling. So zinc might react faster than hydronium under some conditions.

ChemTalk - 14-2-2021 at 18:15

Quote: Originally posted by clearly_not_atara  
It's concentration. In an aqueous solution of zinc sulfate (and nothing else), the concentration of [Zn2+] is probably about ten thousand times that of [H+]. Magnesium reacts very slowly with neutral water, and just barely in weak acids. Only strong acids produce rapid bubbling. So zinc might react faster than hydronium under some conditions.


Yeah, I think it only surprised me because I hadn't read about other people doing it before. It wasn't mentioned on the zinc sciencemadness wiki page.

Regarding reacting with acids, we just produced a video on the reaction of magnesium ribbon with acids, and like you said it reacts fairly quickly with strong acids (strong from a Ka perspective), even when they are quite dilute. I believe the reaction with weak acids may be slow due to the passivation layer, not its inherent reactivity.