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galvanic cells are stupid
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| Turbonium |
You guys know the answer to this?:
In a Zn and Cu galvanic cell (Zn is the anode, Cu is cathode, electrons flowing from anode to cathode, with Cu plating onto the Cu electrode, and the Zn electrode being "eaten" away), what is the black residue that forms on the Zn electrode?
Here's the setup of the cell (except in mine I'm using a porous cup and not a salt bridge): http://web.fccj.org/~ethall/2046/ch18/galvanic.htm |
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| moncster |
omg drug synth discussion
ban plz |
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| Mako |
| Might be the zinc sulphate that has low solubility in water, but i'm not sure, go check for it's solubility in your book. |
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| montie |
well the zinc atoms are losing their electrons thus leaving the atoms positivly charged leaving them open to be bounded to by the SO4
so it could be ZnSO4 accumulating?
i dunno tho. thats my crazy answer, i should know this, cuz im at about the same point in my chem clas. |
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| Turbonium |
I figured it out. It's Zn(OH)2 (solid). The SO4 in the soln acts as a base, and rips H off the H2O in soln. This leaves OH, blablabla, ug et the picture. The one thing is tho, u need two H for every SO4, so eek, I dunno... (do the math to figure out what I mean, too lazy to explain)
btw guys, all sulphates are aqueous... |
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| Turbonium |
Ok, another thing, cuz right now I'm tired and not thinking straight...
"What is the purpose of keeping both the Zn and Cu electrodes in their respected solutions?"
I thought of a few things, but I don't think they're right... |
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| daffodil |
that allows the oxidation and reduction reactions to occur. i can't remember the scientific explanations because i haven't had chemistry in a couple years. basically, the electrons need a destination and you need to be able to create a need or pull for the electrons. there's an explanation in your textbook because i'm doing a very poor job of explaining.
edit: got my mind working again. you need the separate solutions becaues the different charges created by the oxidation of zinc cause the electrons to flow across the salt bridge and reduce the copper. if they are in the same solution, the zinc will not oxidize. the two solutions are a different charge and the point is to see electron flow through a solid between solutions, hennce separate solutions. i think you could add copper ions to solid zinc and get the same result. actually, i think i remember an experiment involving that. |
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| Turbonium |
This is what I said, don't know if it's right:
The two half-cells must be kept in their own separate containers because, if the two separate solutions in each were to be mixed, Zn will be plated onto the Cu electrode alongside the Cu being plated. If the aim of the galvanic cell was to electroplate copper onto the copper electrode, this would defeat the purpose, as the copper plated would be full of impurities (Zn atoms).
Also, by mixing the two solutions together, the electrons would not travel through the wire (or intended circuit), but through the solution instead (assuming low enough resistance in solution). The whole purpose of a galvanic cell is to provide power for something, via the wire leading from the anode to cathode (ex. light bulb). Therefore, mixing the two solutions together would defeat the purpose of the galvanic cell. |
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| Trancention |
| After reading all of that...I actually remember chemistry..:eyes: |
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