how do standard electrode potencial help us understand if certain reagents will react in a redox reaction

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I am a high school student and I am having trouble understanding how standard electrode potencial helps us see which reagents will react or not in a redox reaction

My chemistry book gave the example of the H+ and copper explaining that since copper has a lower reduction power than the H2 they don’t react. I didn’t understand the reason behind it.

Let’s say that A has a weaker reduction power than B, does that mean that A and B don’t react? But if A has a weaker reduction power than B, then it means that B has a stronger reduction power than B, so does that mean that B and A react?

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Anonymous 0 Comments

There’s a little more to it than that, because there are two ways something can ‘react’:

* it can have higher reduction potential, and take electrons, or
* it can have lower reduction potential, and give electrons.

For a redox reaction, we need one of each.

In your example, H+ is (potentially) an oxidizing agent (it has room to take electrons, and do 2H+ + 2e- –> H2). And copper metal is potentially a reducing agent (it has electrons it could give away, to do Cu –> Cu2+ + 2e-).

But the other ingredient is, if hydrogen is going to take electrons away from copper, it has to be stronger than copper, i.e. ranked higher on the redox table, so it can pull those electrons off of copper. And it’s not. Hydrogen’s reduction potential is 0.00V and copper’s is 0.34V. (I hope that matches your data book.) So we’re not going to get a reduction; hydrogen isn’t strong enough.

If you try that again with H+ and, say, zinc, now we have all the requirements for a reaction:

* H+ wants electrons; it’s an OA
* Zn has electrons to give; it’s an RA
* H+ has a higher reduction potential than Zn so it’s strong enough to rip Zn’s electrons off

…game on. Those substances will react on contact.

That help at all?