Description of experiment
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Needed compounds:
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nitric acid : HNO3
sulphuric acid : H2SO4
sodium borohydride : NaBH4
copper sulfate penta hydrate : CuSO4 . 5H2O
Class:
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elem=Cu
redox
Summary:
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Borohydride is capable of reducing copper to its metallic state.
Description:
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Add a solution of NaBH4 to a solution of copper sulfate: A lot of gas is
produced and a dark curdy brown/black precipitate is formed.
Rinse the precipitate a few times with tap water and then decant the water.
Next add dilute H2SO4 (appr. 20% by weight): The precipitate does not
dissolve in the dilute acid.
Decant the liquid and add some HNO3 (appr. 50% by weight): Now the dark
brown precipitate quickly dissolves. The liquid becomes blue and the gas
mixture above the liquid becomes brown.