Your help would be greatly appreciated! :) A solution is saturated with H2S at a
ID: 750433 • Letter: Y
Question
Your help would be greatly appreciated! :)
A solution is saturated with H2S at a concentration of 0.10 M and is 4.0*10^-5 M in each of the metal cations Co2+, Fe2+, Mn2+, Ni2+, and Zn2+. At a pH of 4.0, which of the metal cations will precipitate as the sulfide? Explain. (HINT: Calculate IP)
Metal SulfideKspA
ZnS 3*10^-2
NiS 0.80
CoS 3
FeS 6*10^-2
MnS3*10^10
Under the conditions given, what pH is needed to precipitate as much of the Zn2+ and Ni2+ as possible without precipitating the Co2+, Fe2+, and Mn2+?
Under the conditions given, at what pH will the FeS first begin to precipitate from solution?
Explanation / Answer
Fe2+ + S2- --> FeS 2 Cr3+ + 3 S2- --> Cr2S3 Ni2+ + S2- --> NiS Ionic formulas should be balanced according to charge. FeS and NiS are easy because the charges are equal and opposite. With Cr3+ and S2-, you need to balance the charges so that they are +6 and -6 (Cr2S3)
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