Description of experiment
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Needed compounds:
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nitric acid : HNO3
sodium hydroxide : NaOH
sodium persulfate : Na2S2O8
hydrogen peroxide : H2O2
lead nitrate : Pb(NO3)2
Class:
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elem=Pb,O
redox
precipitation
Summary:
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Lead hydroxide is oxidized by hydrogen peroxide. The resulting compound
does not dissolve in dilute nitric acid.
Description:
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Sequence 1:
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Add a dilute solution of sodium hydroxide to a solution of lead nitrate:
Formation of a white precipitate.
Add some H2O2 (3% solution): The precipitate becomes brown/sepia. A small
amount of oxygen is evolved.
Add an excess amount of nitric acid (2 mol/l): No visible changes of color
of the precipitate, it does not dissolve. The structure of the precipitate
appears to change a little.
Sequence 2:
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Add a dilute solution of sodium hydroxide to a solution of lead nitrate:
Formation of a white precipitate.
Add some solid Na2S2O8: The precipitate becomes yellow/ochre. The complete
change from white to yellow/ochre takes approximately 1 minute.
Add an excess amount of nitric acid (2 mol/l): The color of the precipitate
changes to brown/sepia, the same as the color, observed in sequence 1.