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International Hazard
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Metal displacement reactions
what i have never understood is if these reactions are actually useful for metal precipitation
For example, if I want to precipitate copper from CuSO4 with an iron nail, is the iron nail going to get plated and passivated with copper and just
stop the reaction, or is the copper going to fall off the iron and dissolve the nail completely?
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MrHomeScientist
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It depends on the metals you are using. In most cases I don't believe plating happens - that usually requires some pretty careful setup to get a nice
metal plate. I think in your example copper coats the nail in a rough coating that continues to grow into a spongy-looking mass if left in the
solution (at least, that's been my experience). Precipitating silver from silver nitrate with copper wire (the classic silver tree demo) results in
very pure silver that falls right off the wire when lightly tapped.
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tetrahedron
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you can ensure complete dissolution of the iron by making it the anode (+) of an electrolytic cell (keep the voltage as low as you can). pure copper
will then 'plate' out (most likely in a spongy form, unless other measures are taken) at the cathode (pure copper, such as electrical wire, is
preferred as the cathode). once oxidized, the iron will remain in solution. once hydrogen starts bubbling at the cathode, most of the copper ions have
been reduced. as the hydrogen ions get reduced, the electrolyte will becomes more basic, so watch out for the formation of insoluble basic iron
compounds (add some dilute sulfuric acid before you start, or wash the copper precipitate with it).
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platedish29
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COat it with zinc -> copper -> silver, chrome, nickel in this sequence if you want to get anything coated.
If you have problems with the first coating, you'll have problems with all the others too x) hehe
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