Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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sodium hydroxide : NaOH
sulphuric acid : H2SO4
sodium persulfate : Na2S2O8
ammonium persulfate : (NH4)2S2O8
nickel sulfate : NiSO4 . 6H2O
Class:
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elem=Ni,O
precipitation
redox
Summary:
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Nickel (II) gives a black precipitate when treated with hydroxide and
persulfate at the same time. It is expected that this is an higher
oxide of nickel (NiO2).
Description:
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Dissolve some nickel sulfate and some ammonium persulfate in water: The
resulting liquid becomes pale green, just as a solution of nickel sulfate
without the persulfate.
Add a solution of sodium hydroxide: A black precipitate appears, also
without heating (at a temperature of appr. 15 C).
Add an excess amount of dilute sulphuric acid (appr. 10% by weight): The
black precipitate dissolves, the liquid becomes almost clear and pale
grey/green. A gas is evolved. The gas is odourless.
The same set of experiments is performed with Na2S2O8. The same result is
observed for the sodium salt.