Which ion will be oxidized/reduced?


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klarratt2
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Joined: Fri Sep 28, 2018 12:16 am

Which ion will be oxidized/reduced?

Postby klarratt2 » Thu Feb 21, 2019 11:54 am

If we are just given which ions are used in the reaction, how would we be able to tell which one is oxidized and which is reduced? For example, if a question just told us we had Cu^2+ and Zn^2+, how would we know that Cu is reduced and the Zn^2+ has been oxidized?

A De Castro 14B 2H
Posts: 75
Joined: Fri Sep 28, 2018 12:29 am

Re: Which ion will be oxidized/reduced?

Postby A De Castro 14B 2H » Thu Feb 21, 2019 12:01 pm

One can tell which ion will be oxidized or reduced based on their standard reduction potentials, E°. A solution with a more positive reduction potential will tend to gain electrons (i.e. to be reduced by oxidizing the new species). Meanwhile, a solution with a more negative reduction potential will tend to lose electrons (i.e. to be oxidized by reducing the new species).

In your question, E°(Cu2+) = +0.339 V while E°(Zn2+) = -0.762 V. Since E°(Zn2+) is more negative than E°(Cu2+), Zn2+ has been oxidized.


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