How Does Hydrogen Sulfide Affect pH and Precipitation in a Cu-Zn Solution?

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SUMMARY

The discussion focuses on the effects of hydrogen sulfide (H2S) on pH and precipitation in a solution containing Cu2+ and Zn2+ ions, each at a concentration of 0.1M. H2S, a weak diprotic acid, dissociates in the solution, influencing the pH primarily through its first dissociation step. To determine the final pH and the potential for precipitation, one must calculate the concentration of sulfide ions (S2-) and compare it against solubility product constants (Ksp). The discussion emphasizes the importance of using the correct equilibrium equations for accurate calculations.

PREREQUISITES
  • Understanding of weak acids and their dissociation, specifically H2S as a diprotic acid.
  • Knowledge of equilibrium constants and their application in chemical equilibria.
  • Familiarity with solubility product constants (Ksp) for precipitation reactions.
  • Basic skills in calculating pH from concentrations of ions in solution.
NEXT STEPS
  • Study the dissociation equations for hydrogen sulfide (H2S) and its impact on pH.
  • Learn how to calculate the concentration of sulfide ions (S2-) in solution.
  • Research solubility product constants (Ksp) for copper and zinc sulfides to assess precipitation conditions.
  • Explore the pH calculation methods for polyprotic acids and their implications in solution chemistry.
USEFUL FOR

Chemistry students, chemical engineers, and professionals involved in solution chemistry and precipitation processes will benefit from this discussion.

dragonlady90
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Homework Statement


A sol'n contains Cu+2(aq) and Zn+2 ions each at a con'c of 0.1M. Hydrogen sulphide gas is bubbled up into sol'n and dissociates having an initial con'c of 0.1M. Whats the pH of the final solution? Will any precipate form?
I don't know how to start the problem. Pls help me and reply soon.

Homework Equations





The Attempt at a Solution

 
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H2S is a weak diprotic acid. Differences between both dissociation constants are large enough to calculate each dissociation equilibrium separately. You have to check what the pH is (it i will be solely governed by the first dissociation step), use this pH value to calculate S2- concentration, and check if this concetration will be large enough for precipitation (hint: look for Kso values).

For more details see this page on the pH of polyprotic substance calculation.
 
thanks for your reply Borek,

can u tell equation of this equilibrium problem so that i can solve it further. THat would be really helpful.
Once again, thanks for your reply.
 
All equations that you need to calculate pH of the solution and S2-[/sup concentration are listed on my site.
 
Are you still having problems with this question?
 

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