Treason
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CuSO4 electrolisis
Could someone help me?
I'm studying chemistry but something anoying just happened when I was depositing Cu by the electrolisis of CuSO4. I used a Graphite electrode and made
twice the experience. The first time I obtained 0.03g above what I should, so I made it once again, (with the teacher next to me) and obtained 0.023g
below what I should.
Is there a reason for that? I dried the graphite after depositing the Cu so I don't know where could I be wrong.
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woelen
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The experimental conditions must be very precisely determined in order to check the charge/mass ratio. You should precisely measure the current as
function over time (integral of current over time equals the total charge). Also, you should be sure, that there is no side reaction, in which
hydrogen is formed. You even may have some hydrogen, absorbed into the metal, making it weigh less than you would expect. This kind of experiments is
very hard to perform precisely. Best would be to have a current logging (e.g. every few seconds, you measure the average current over the past unit of
time) and use the integrated value for computing the expected amount of plated copper.
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Waffles
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Stone knives and bear skins. Experimental error. Human error. This should be moved to Beginnings.
\"…\'tis man\'s perdition to be safe, when for the truth he ought to die.\"
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The_Davster
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You have to go into more detail about the equipment used, electrolysis experiments can be either very simple and not quantitative, or really complex
with colombmeters and such. Without all the fancy equipment, I would not be expecting exact yields. Unfortunatly, electrolysis has all sorts of
physics behind it which make it a bit more difficult than two electrodes in a solution. Without all the stuff Woelen mentioned, I would not expect
yields precise to within 0.01g, which it seems you are expecting.
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Treason
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I never tought that hydrogen could do things like that. I'll have to review all what we done once again and search where the error can be (Even when
it can be everywhere or in more than in one place at the same time).
Thank you a lot. I'll keep reading.
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Magpie
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How much did you expect to get?
The single most important condition for a successful synthesis is good mixing - Nicodem
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Ozone
International Hazard
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Hello,
Radio Shack was selling a very cool multimeter (self scaling, too) which compared well with my Fluke, AND, has a serial output. It comes with a very
intuitive software package called "Meter View"tm which seems to work on win 95, 98, 2000, and XP (have not tried XP-64 or Vista beta). It gives you a
nice graph, and outputs to ASCII wich is simple to import into Excel as a CSV. It cost me about $70 US imagine that, a Radio Shack product that is
worth every penny.
You should use this to measure the current and cell voltage. The cell voltage can be used (look up the Nernst equation, viz. not-so-fun-damentals) to
determine if the redox you are trying to do is even possible, and if it is, the current can be used to calculated the amount of metal deposited per
unit of time.
Good luck, keep trying,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Quibbler
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Copper sulphate electrolysis should work, but you need to be careful.
A small current for a long time is what is required.
A large current and the CuSO4 concentration around the electrodes will diminish and other reactions will take place.
The conditions I use are 6 g of CuSO4.5H2O in 100 g H20 and a current of 10 mA regulated (with a LM317) for 2 hours.
Even so the cathode reaction is often not as pure as I would like.
If you can degassing the solution also helps.
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