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

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Discussion Overview

The discussion revolves around the effects of hydrogen sulfide on the pH and precipitation behavior in a solution containing copper (Cu2+) and zinc (Zn2+) ions. The context is primarily homework-related, focusing on the calculation of pH and potential precipitation of sulfide ions.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant states that H2S is a weak diprotic acid and suggests that the dissociation constants are significant enough to calculate each dissociation equilibrium separately.
  • Another participant is seeking guidance on the equilibrium equations necessary for solving the problem, indicating a need for further clarification on the topic.
  • A participant mentions the importance of checking the pH, which they believe will be governed by the first dissociation step of H2S, and suggests using this pH to calculate the concentration of S2- ions.
  • There is a reference to looking up solubility product constants (Ksp) to determine if precipitation will occur.
  • One participant offers a resource with equations needed for calculating pH and S2- concentration.

Areas of Agreement / Disagreement

The discussion does not present a consensus, as participants are at different stages of understanding the problem, with some seeking more information while others provide technical insights.

Contextual Notes

Participants have not fully resolved the mathematical steps necessary for calculating pH and precipitation, and there are dependencies on specific equilibrium constants and definitions that remain unaddressed.

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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