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Name: Michael Leyba  (mleyba) 
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1999 

A student in my class, Noreen, asks "What happens to Copper Sulfide or Copper Sulfate when you mix it with an acid (Hydrochloric or Sulfuric)?" Noreen is nine years old and this is a computer class. We are demonstrating the power of networks. This is not a chemistry class. Thanks to anyone who knows the answer.

Hi Noreen and Michael -

First of all, Copper Sulfide will behave quite differently than Copper Sulfate. Sulfides will not dissolve in water, while sulfates usually particular, copper sulfide will not dissolve, but copper sulfate will dissolve. Now, when you consider the effeect of adding acid to copper sulfate, well, I would expect that the main effect would be that the copper sulfate would be easier to dissolve, because addition of acid will cause a reaction with sulfate ions to form HSO4-, and by LeChatelier's principle that should dissolve fore of the solid copper sulfate.

Short I believe that adding weak acid to copper sulfate will cause it to readily dissolve. I also believe that adding weak acid to copper sulfide will not do much of anything.

[Note: the above is an "educated guess" and may be off a bit.]


Just to add to Dr. Topper's I tend to think that by adding acid to copper sulfide, it will dissolve. I'll invoke LeChatelier also here. Addition of acid should form hydrogen sulfide...a weak acid that won't dissociate completely (redundant, I know). So as more sulfide ion is made into H2S, the copper sulfide should dissolve.

CuS ---> Cu2+ + S2-
S2- + 2H+ <===> H2S


I believe that copper sulfide is one of the few metal sulfides that will not form hydrogen sulfide upon the addition of a weak acid. We use a very sensitive Gas Chromatography method that can detect sulfide in the sub-picomolar range by converting it to H2S by addition of acid. Copper sulfide is NOT detectable by our method because the acid cannot convert the sulfide to H2S.


This sounds like current research, right off the afterburner....! Thanks for the help, Stacie.


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