Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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ammonia : NH3
hydrochloric acid : HCl
sodium hydroxide : NaOH
hydroxyl amine sulfate : (NH3OH)2 SO4
copper sulfate penta hydrate : CuSO4 . 5H2O
Class:
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elem=Cu
redox
precipitation
Summary:
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Hydroxyl amine sulfate (containing protonated hydroxyl amine) is not capable
of reducing copper (II). When the liquid becomes basic (releasing free
hydroxyl amine), then the copper (II) is reduced to copper (I).
Description:
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Add a solution of copper sulfate to an excess amount of a solution of
hydroxyl amine sulfate: The liquid becomes blue, no visible reaction occurs
between copper (II) and hydroxyl ammonium.
Add an excess amount of a solution of NaOH: Formation of a dark green/blue
precipitate, which quickly turns yellow/brown. A colorless and odorless gas
is evolved (is this N2 or N2O?).
Add an excess amount of HCl (10% by weight): The liquid becomes white/milky
for a moment, but within 2 seconds it becomes completely clear and colorless.
Add an excess amount of NH3 (5% by weight) to the liquid with the dark green/
blue precipitate: The precipitate does not dissolve nor does it change color.