Description of experiment
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Needed compounds:
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nitric acid : HNO3
hydrogen peroxide : H2O2
sodium bicarbonate : NaHCO3
silver nitrate : AgNO3
Class:
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elem=Ag
precipitation
Summary:
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Silver (I) gives a precipitate with bicarbonate, which becomes yellow and
more compact on standing. With H2O2 a dark compound is formed, which
dissolves in nitric acid under formation of a gas. Is this dark compound
a higher oxide of silver (e.g. Ag2O2?).
Description:
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Add a solution of sodium bicarbonate to a solution of silver nitrate: A
pale yellow precipitate is formed.
Let stand for a few days: The color of the precipitate has shifted from
almost white to yellow like sulphur. The precipitate has become more compact.
Decant the liquid from the precipitate and add some hydrogen peroxide (30%
by weight) to the precipitate with the remaining part of the liquid: The
liquid starts foaming violently and the liquid becomes very hot. The
precipitate becomes dark grey, almost black. A white fume is produced
(condensed vapor of water?).
Add a small amount of HNO3 (appr. 50% by weight): The precipitate dissolves
again, the liquid becomes light yellow/brown and remains a little turbid.
While the precipitate dissolves, a colorless gas is produced.