Description of experiment
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Needed compounds:
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hydrogen peroxide : H2O2
sodium hydroxide : NaOH
sodium persulfate : Na2S2O8
nickel sulfate : NiSO4 . 6H2O
Class:
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elem=Ni,O
precipitation
redox
Summary:
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Hydrogen peroxide probably serves as a reductor for an higher oxide of
nickel.
Description:
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Set of experiments 1
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Add a solution of NaOH to a solution of nickel sulfate: A pale green
precipitate appears.
Add some solid sodium persulfate: The pale green precipitate turns black.
Add some H2O2 (3% solution): A gas is evolved and the precipitate turns
pale green again.
Set of experiments 2
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Add a solution of NaOH to a solution of nickel sulfate: A pale green
precipitate appears.
Add some H2O2 (3% solution): At first sight nothing happens. After appr.
1 minute a gas is evolved slowly. The color of the precipitate does not
change.
Add some solid sodium persulfate: More gas is evolved, much more bubbling.
The color of the precipitate does not change.
Remark: The addition of hydrogen peroxide prevents the formation of a black
precipitate when nickel hydroxide and persulfate are combined. When a black
precipitate exists, then it is destroyed by hydrogen peroxide. Probably
hydrogen peroxide acts as a reductor on the black precipitate (which
most likely will be a higher oxide of nickel, NiO2).