Description of experiment
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Needed compounds:
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copper sulfate penta hydrate : CuSO4 . 5H2O
sodium azide : NaN3
Class:
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elem=N,Cu
precipitation
coordination
Summary:
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Copper(II) ions and azide ion give rise to formation of an intensely dark
colored precipitate/complex.
Description:
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Prepare a solution of sodium azide in water. Only use a very small amount. Mix
this solution with a solution of copper sulfate: A very dark brown precipitate
is formed. It is really amazing to see how intense the color of this
precipitate is. The solution also obtains a very dark color.
Probably, this is Cu(N3)2, and apparently, this compound/complex is somewhat
soluble, such that its solution has a sufficiently high concentration to give a
strong brown color to the solution.
Add a few drops of hydrochloric acid to the liquid with the dark brown
precipitate: The precipitate dissolves, the liquid becomes light blue again.
WARNING: Do not attempt to isolate and dry the dark brown compound. It is
highly explosive. Also perform the experiment with really small quantities (a
few granules of a cubic mm or so is sufficient).