Description of experiment
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Needed compounds:
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hydrogen peroxide : H2O2
hydroxyl amine sulfate : (NH3OH)2 SO4
ammonia : NH3
copper sulfate penta hydrate : CuSO4 . 5H2O
Class:
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elem=Cu,N
redox
Summary:
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Copper (II) amine complex is reduced to a colorless copper (I) amine
complex by hydroxyl amine. The copper (I) complex is oxidized by oxygen
from the air very easily.
Description:
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Add a large excess amount of ammonia (appr. 5% by weight) to a solution of
copper sulfate: The liquid becomes intense blue, after an initial formation
of a sky-blue precipitate, which quickly redissolves.
Add an excess amount of hydroxyl amine sulfate (relative to the copper
sulfate): The solid dissolves and while it dissolves, the liquid becomes
lighter. The liquid becomes almost colorless. The change of color is not
momentaneous.
Shake the liquid with contact with air: Liquid becomes blue again.
Dilute the liquid (at least 20 times) with water: The liquid becomes colorless,
no blue hue can be observed anymore.
Add a small amount of H2O2 (appr. 10% by weight): Formation of dark brown/
green turbid clouds. When the liquid is shaken, it becomes dark green and
turbid. This color, however, quickly changes and after approximately 1 minute
the liquid has turned completely clear and it has a beautiful deep bright
blue color.