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

  • Thread starter SDTK
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  • #1
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Main Question or Discussion Point

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?
 

Answers and Replies

  • #2
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If it causes discomfort to the eyes, it is not hydrogen. That only leaves one possibility...
 
  • #3
symbolipoint
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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
 
  • #4
Borek
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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.
 
  • #5
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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
 
  • #6
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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
 
  • #7
hilbert2
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It could be carbon dioxide if some copper carbonate had formed on the coins as a result of corrosion.
 

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