Metal finishing Q&As since 1989

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Electrolysis of copper sulphate in soil

February 2, 2010

Dear sir:

I am a 10th grade chemistry student in high school. For a project, I have been saturating soil with a copper sulphate [on eBay or Amazon]solution and performing electrolysis on the sample. I find a buildup of copper upon the anodes, and small blue particles speckled throughout the sample. Am I right in assuming that these small blue particles are Copper hydroxide? What happens to the sulfur in the equation:

CuSO4 + H2O -> Cu + CuOH + ?

Yours truly

Meg V
student - Plano

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First of two simultaneous responses --

Meg,
CuOH is yellow. Cu(OH)2 is a blue gel or powder.
You can look up all of the possible copper compounds in a reference book like Langes or the Chem. Rubber Handbook of chemistry and physics. They should have this at the public library if your school does not have it. Check with all of the chemistry teachers also. Surely, one will have one.
If you can find a larger crystal, handle it with care and look at the crystal shape under a low power scope-say 20 to 40 X. I think that you will find that it is copper sulphate that has crystallized out from the amount of excess that you put in it.
If you would like additional comments, get my email from Ted and send me what you have written so far. I am sort of kind, but rather critical, depending on how correct it is that you need this to be. I am a retired chemist and a certified chemistry teacher. I love well done science projects.
Jim

James Watts
- Navarre, Florida
February 3, 2010

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Second of two simultaneous responses -- February 4, 2010

Meg,

First problem - look at your chemical equation. What is going to drive this equation to the right? In my experience you would need severely forcing conditions to drive the reaction, look up activation energies and you'll see why it won't work.

Second problem - little blue flecks in your soil sample. What color was the solution you added? Have you tried evaporating to dryness a small sample of your solution and see what happens. I think that will answer your questions nicely.

Brian Terry
Aerospace - Yeovil, Somerset, UK