What is the true voltage of a voltaic cell?

[Seeit]

TL;DR Summary

Hello,
What is the voltage of a voltaic cell? Should it be determined from the difference of the potentials of zinc and copper or zinc and hydrogen?

Hello,
What is the voltage of a voltaic cell? Some sources claim it's 1.1 V (the difference of potentials of zinc and copper). But I've also seen its being claimed to be 0.76 V (the difference of potentials of zinc and hydrogen). I know that zinc and hydrogen are the ones undergoing redox reactions and the copper only acts as a conductor, so to me, the value 0.76 V seems more logical. But what is it then with 1.1 V? What is the truth?

 

[BvU]

copper only acts as a conductor

in a galvanic cell the copper isn't just a conductor.

$\$

 

[Seeit]

in a galvanic cell the copper isn't just a conductor.

$\$

I meant the cell in the voltaic pile (https://en.m.wikipedia.org/wiki/Voltaic_pile). Wikipedia here itself says that the copper is only a conductor and hydrogen is the one reacting. The Wikipedia page mentions the voltage of 0.76 V.
Well, as voltaic cell itself can mean both the galvanic cell in general and the one created by Volta, this could cause the ambiguity.
But I asked about the voltage of the voltaic cell created by Volta containing sulfuric acid. I thought someone here would know.

 

[willem2]

in a galvanic cell the copper isn't just a conductor.

$\$

If you want that, you must use a solution of a copper salt, so copper metal can precipitate on the electrode. If you just use acid or brine, there's no way for the copper to participate in any reaction.

 

[BvU]

I meant the cell in the voltaic pile

My bad googling . Voltaic cell gets galvanic cell. Voltaic pile gets, well, voltaic pile. Would have gone better if you had included thte link in post #1.

$\$

 

[Borek]

If you just use acid or brine, there's no way for the copper to participate in any reaction.

Unless it gets oxidized.

 

[Seeit]

If you want that, you must use a solution of a copper salt, so copper metal can precipitate on the electrode. If you just use acid or brine, there's no way for the copper to participate in any reaction.

Yes, I agree. So the voltage of a voltaic pile's one cell should be 0.76 V? Why do some pages mention 1.1 V? For example Czech Wikipedia mentions 1.1 V for this cell, should I edit it then?

 

[willem2]

Unless it gets oxidized.

To get a battery we must have oxidation at one electrode and reduction at the other. The zinc is what gets oxidized, so copper must be reduced, so you'll have to start with Cu⁺.

 

[Borek]

To get a battery we must have oxidation at one electrode and reduction at the other. The zinc is what gets oxidized, so copper must be reduced, so you'll have to start with Cu⁺.

In Zn/Cu battery, yes, Zn is getting oxidized, copper is getting reduced, no doubt about it. But technically it is possible to make a battery which works by oxidizing copper, just a matter of selecting something that will be reduced at a potential high enough (Ag⁺/Ag will do the trick). Your original claim

If you just use acid or brine, there's no way for the copper to participate in any reaction.

seems to be suggesting it is not possible at all.

 

[dlgoff]

My go to place for batteries:
https://batteryuniversity.com/

 

[tech99]

The Daniel Cell gives 1 volt approx and uses copper and zinc. I think the Volt was originally defined from this type of cell.