What gas is produced when copper is added to diluted HCl?

[SDTK]

Copper pennies were placed into HCl which had been diluted with an unknown quantity of water.

The pennies look cleaner, ... remain un-corroded (as expected). There is a slight bit of gas being produced , with no smell, but can cause discomfort to eyes. Bubbles formed on the pennies for the first 2 days.

-- What is the gas?

-- Could it be a product of reaction with the HCl and any oils, "dirt" that was on the pennies?

 

[Gene Naden]

If it causes discomfort to the eyes, it is not hydrogen. That only leaves one possibility...

 

[symbolipoint]

Some HCl may come out from solution as HCl gas which may irritate your eyes. The gas from bubbles you saw happening might be Hydrogen gas, H₂.

Cu + 2H+ ---------> Cu⁺² + H₂

 

[Borek]

Equilibrium concentration of Cu²⁺ in the presence of non-oxidizing acid is in the 10^-11 M range, I don't think that's enough for the bubble formation.

 

[SDTK]

Some HCl may come out from solution as HCl gas which may irritate your eyes. The gas from bubbles you saw happening might be Hydrogen gas, H₂.

Cu + 2H+ ---------> Cu⁺² + H₂

thank you

 

[SDTK]

Equilibrium concentration of Cu²⁺ in the presence of non-oxidizing acid is in the 10^-11 M range, I don't think that's enough for the bubble formation.

thank you

 

[hilbert2]

It could be carbon dioxide if some copper carbonate had formed on the coins as a result of corrosion.