Mixture of Copper Sulfate with an Acid?
Name: Michael Leyba (mleyba)
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 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
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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Update: June 2012