Description of experiment
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Needed compounds:
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sulphuric acid : H2SO4
sodium hydroxide : NaOH
copper sulfate penta hydrate : CuSO4 . 5H2O
Class:
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elem=Cu
precipitation
Summary:
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Copper hydroxide easily looses water, when it is heated, even if it is
completely covered with water.
Description:
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Prepare a solution of copper sulfate and prepare a solution of sodium
hydroxide. Add both solutions to each other: A blue precipitate is formed.
This precipitate is hydrous copper hydroxide.
Heat the liquid with the blue precipitate: Fairly quickly, the precipitate
turns black. The blue copper hydroxide turns into dark brown/black copper
(II) oxide.
Add an excess amount of dilute sulphuric acid: The black solid slowly
dissolves. It does not dissolve as fast as a fresh precipitate of blue copper
hydroxide, but in a few minutes, however, all of the black precipitate has
dissolved. The liquid becomes light blue and clear.