Steve_hi
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Excess of reactants
I'm reacting some copper wire with Hno3 to have some copper nitrate and I was wondering
1) if it is best to have the stoichiometric amount or to have one of the reactants in excess.
2) Is this always the case when doing reactions.
Sorry to bother you with simpleton questions but I have never taken chemistry and trying to learn at home
Thanks
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Hockeydemon
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I'm sure someone will correct me if I'm wrong, but I had to jump at the chance to contribute as a novice haha.
If you're reacting copper with nitric acid you should be able to simply pull out any un-reacted copper as it will still be a solid. So excess in this
case is ideal.
It is definitely not always the case, and you will need to come at it on a case by case basis.
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Steve_hi
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Thanks Hockeydemon
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CaptainOfSmug
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Yes, generally speaking you must first find your limiting reagent, I'm assuming you know some basic stoichiometry. Once you've found your limiting
reagent you know to have that one in excess generally speaking. I've found with chemistry there is little "always does this" and its more
"usually". Hope this helps somewhat.
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MrHomeScientist
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In this case, using copper as your excess reagent is good because when the reaction is complete you just remove the solids and you're left with your
pure product in solution. If it was the other way around and the copper dissolved completely, you might have some leftover acid contamination. That
might not be a bad thing, depending on your end use: it's actually sometimes necessary for stability of the produced compound. I think iron chloride
is an example of this, but don't quote me on that.
EDIT: Corrected reversed terminology. D'oh! Thanks for the correction below, elementcollector1.
[Edited on 3-26-2013 by MrHomeScientist]
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elementcollector1
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Shouldn't it be the other way around? The nitric acid is the limiting reactant, running out first and leaving an excess of copper metal behind.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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