Copper + sulfuric acid + H2O = stink?

[Mustard Tiger]

I put some copper bits into concentrated sulfuric acid. Nothing much happened other than it got shiny and clean looking. So I poured off the acid and then put water on the copper to rinse off the remaining acid, and the copper started bubbling and made a nasty rotten egg smell. Is that hydrogen sulfide or sulfur dioxide or what? What chemical reactions happened here?

 

[magoo]

Do a search on rotten egg smell.

 

[Borek]

Is that hydrogen sulfide

Yes.

What chemical reactions happened here?

Most likely the copper surface was covered with traces of sulfide earlier. While technically it is possible for the sulfuric to be reduced by copper, I don't think it will go that far.

 

[hilbert2]

I think elevated temperatures are needed for sulfuric acid to be reduced to sulfur oxides by copper. That kind of heating can be caused by sudden dilution of the acid, in principle.