Description of experiment
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Needed compounds:
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sodium persulfate : Na2S2O8
nitric acid : HNO3
silver nitrate : AgNO3
Class:
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elem=Ag
redox
Summary:
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Silver (I) reacts with persulfate. Probably a higher oxidation state of
silver is produced (oxidation state II or III).
Description:
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Add some solid Na2S2O8 to a solution of AgNO3 in HNO3 (appr. 1% AgNO3 in
10% HNO3): The solid dissolves, the liquid becomes brown. This reaction
is not immediate, but takes approximately 10 seconds. Finally, the liquid
is clear and dark brown. Is this dark brown color the color of silver (II)
or silver (III) ions? Slowly, a gas is evolved throughout the liquid. Minute
bubbles slowly move up to the surface of the liquid.
Heat the liquid until it starts boiling: The evolution of gas becomes more
vigorous. At a certain moment, the evolution of gas suddenly ceases. At that
point, the liquid is light brown. When the liquid is heated for a longer time,
then no visible changes occur.
Add some solid Na2S2O8 to the still hot liquid: The solid quickly dissolves
while a gas is evolved. The liquid becomes darker brown, but not as dark as
it was at the start of this experiment.