Here's the simple voltaic cell that I have...

 

One copper electrode and one zinc electrode immersed in a sulfuric acid electrolyte. There is an external load between the electrodes.

 

The sulfuric acid ionizes into hydrogen ions and sulfate ions. H₂SO₄ ---> 2H⁺ + SO_4^2-

 

The sulfate ions migrate to the zinc electrode and oxidizes the zinc. Zn ---> Zn²⁺ + 2e-

 

The 2 extra electrons stay on the zinc electrode and build up a potential.

 

The hydrogen ions migrate to the copper electrode, strip 2 electrons off each copper, and form hydrogen gas. 2H⁺ + Cu ---> H₂ + Cu²⁺

 

The excess positive charge on the copper electrode builds up a potential that causes the extra electrons on the zinc electrode to flow to the copper electrode and power the load.

 

 

Here's my question...

 

Why do the hydrogen ions strip electrons from the copper electrode and not from the zinc electrode? Likewise, why do the sulfate ions oxidize the zinc on the zinc electrode and not the copper from the copper electrode? I have a feeling this has something to do with standard electrode potential but I'm not exactly sure how it fits in.

 

Any insight would be appreciated.

In other words, why do the reactions in the cell spontaneously occur the way they do?