Description of experiment
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Needed compounds:
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sodium hydroxide : NaOH
copper sulfate penta hydrate : CuSO4 . 5H2O
hydrogen peroxide : H2O2
pyrogallol : C6H3 (OH)3
Class:
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elem=C,Cu
redox
Summary:
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It appears that copper (II) ions catalyse the oxidation of pyrogallol by
hydrogen peroxide.
Description:
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Add a few drops of H2O2 (3% by weight) to a solution of pyrogallol: Liquid
remains colorless and clear. No bubbling. After a few minutes the liquid
still is clear and colorless.
Add a little quantity of solid copper sulfate: The liquid quickly turns dark
brown, although not momentarily. The darkening of the liquid has completed
long before most of the copper sulfate has dissolved.
Add some solid NaOH: The solid dissolves and the liquid turns very dark brown/
red, almost black.