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

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Discussion Overview

The discussion centers on the gas produced when copper is added to diluted hydrochloric acid (HCl). Participants explore the nature of the gas, its potential sources, and the reactions involved, touching on both chemical reactions and observations from an experimental context.

Discussion Character

  • Exploratory
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant notes that the gas produced causes discomfort to the eyes, suggesting it is not hydrogen, leading to speculation about other gases.
  • Another participant proposes that the gas could be hydrogen, despite the discomfort, and provides a reaction equation involving copper and hydrogen ions.
  • Concerns are raised about the equilibrium concentration of Cu2+ in non-oxidizing acids, questioning whether it is sufficient to produce observable bubble formation.
  • One participant suggests that carbon dioxide could be produced if copper carbonate formed on the coins due to corrosion.

Areas of Agreement / Disagreement

Participants express differing views on the identity of the gas produced, with no consensus reached. Some suggest hydrogen, while others propose HCl gas or carbon dioxide as possibilities.

Contextual Notes

There are unresolved assumptions regarding the concentration of reactants and the specific conditions of the experiment, which may affect the gas production and its identification.

SDTK
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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?
 
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If it causes discomfort to the eyes, it is not hydrogen. That only leaves one possibility...
 
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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
 
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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.
 
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symbolipoint said:
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
 
Borek said:
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
 
It could be carbon dioxide if some copper carbonate had formed on the coins as a result of corrosion.
 

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