Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Mixture of Copper Sulfate with an Acid?
Name: Michael Leyba  (mleyba) 
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1999 


Question:
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.



Replies:
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 will...in 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.]

-topper


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

-joe


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.

Stacie


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

-topper



Click here to return to the Chemistry Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory