[SRJ]

I have practically observed that Copper with Concentrated H₂SO₄ at high temperature gives SO₃ but with dilute acid or when cold it only gives H₂.
What is the basic reaction for when H₂SO₄ is
1)Hot and concentrated
2)Hot and dilute
3)Cold and concentrated
4)Cold and dilute ??

[Hunter2]

I don't think you will get any hydrogen with copper and sulfuric acid. Compare the redox potential. Cu/H₂.

Concentrated hot sulfuric will work as oxidizer and gives SO₂ not SO₃. SO₃ will develop if sulfuric is decomposed to water. Has nothing to do with copper or other metals.
1. dissolving copper, SO₂ development
2. nothing
3. very low reaction, probably nothing
4. nothing

[snorkack]

I don't think you will get any hydrogen with copper and sulfuric acid. Compare the redox potential. Cu/H₂.

What is the proton activity that goes to Nernst equation in concentrated sulphuric acid? Is it by any chance the Hammett function?