Description of experiment
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Needed compounds:
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hydrochloric acid : HCl
sodium hydroxide : NaOH
sodium dithionite : Na2S2O4 . 2H2O
copper sulfate penta hydrate : CuSO4 . 5H2O
Class:
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elem=Cu
redox
Summary:
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When copper (II) is reduced by dithionite in neutral environments, then
a dark red/brown precipitate is formed (metallic copper??). When reduced
in alkaline environments, then hydrous copper (I) oxide is formed.
Description:
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Add a freshly prepared solution of sodium dithionite to a solution of copper
sulfate: Formation of a dark red/brown precipitate (copper metal??).
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Add a solution of sodium hydroxide to a solution of copper sulfate: Formation
of a bright blue precipitate.
Add a freshly prepared solution of sodium dithionite: The precipitate almost
instantaneously turns yellow/orange.
Add an excess amount of hydrochloric acid: Formation of a dark brown
precipitate (copper metal??).