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blogfast25
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Interesting. You used a pellet of Zr, not Zr powder, right?
So did the reaction appear self-sustaining after initial heating and initiation?
Did you test for copper (add a little nitric acid: fumes of NOx indicate copper is being oxidised. CuCl2/CuO won’t do that…)?
All in all it seems to prove that CuCl2 + ½ Zr === > Cu + ½ ZrCl4 does proceed as predicted.
Be aware that even if you master an apparatus to capture the ZrCl4, the product will still be highly contaminated with CuCl2, possibly also Cu, and
will require re-sublimation at about 500 C for required purity! This re-sublimation will have to be carried out in the absence of oxygen, as ZrCl4 +
O2 === > ZrO2 + 2 Cl2 is thermodynamically very favourable...
[Edited on 6-2-2011 by blogfast25]
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plante1999
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the reation appear to be self sustaining , i do not test for copper but i will test today.
[Edited on 6-2-2011 by plante1999]
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bbartlog
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The white stuff could also be CuCl. Some CuCl is likely to be present given that you have both Cu and CuCl2 in your residue. And at white heat it's
entirely possible that most of your ZrCl4 escaped as vapor...
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blogfast25
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Nope. There is no reason at all why the reduction should stop at CuCl: CuCl + ¼ Zr === > Cu + ¼ ZrZl4 is also very exothermic and is further
driven by ZrCl4 being driven off.
In a closed system, with a stoichio mix of CuCl2 + ¼ Zr < === > CuCl + ¼ ZrCl4, heated at high temp you would find some CuCl in the reaction
mix (but still mainly Cu and ZrCl4) but not here…
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bbartlog
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I'm sure that's true, but in this case we have
- molar excess of cupric chloride (~22mmol CuCl2 versus 5-6mmol Zr)
- unreacted CuCl2 (as we might expect given the above)
So it seems to me that it's not so much a question of whether the reduction would stop at CuCl if more Zr were available (clearly it wouldn't) but
whether the Zr reacts preferentially with CuCl to such a degree that it would always be consumed before the remaining CuCl2. Of course with the whole
thing open to air CuCl would also tend to be oxidized by atmospheric oxygen, but I don't think its existence here is all that implausible.
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blogfast25
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Hmmm… because the reduction of CuCl2 is much more energetic to Cu than to CuCl, the only real way for CuCl to form is from Cu(s) + CuCl2(s, l?) ===
> 2 CuCl(s), from formed Cu and the excess CuCl2. I don’t know if ΔG < 0 for that reaction. In watery solution CuCl can be made by
boiling a Cu (II) salt with copper wire, and with salt (NaCl) in the solution, so it probably is thermodynamically favourable (driven by the lattice
energy of CuCl). But CuCl oxidises very quickly in air (slower when it’s perfectly dry). No, the white bits he saw was ZrCl4, I’m sure of it…
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