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

[dragonlady90]

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

 

[Borek]

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 S^2- concentration, and check if this concetration will be large enough for precipitation (hint: look for K_so values).

For more details see this page on the pH of polyprotic substance calculation.

 

[dragonlady90]

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.

 

[Borek]

All equations that you need to calculate pH of the solution and S^{2-[/sup concentration are listed on my site.}

 

[chemisttree]

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