Description of experiment
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Needed compounds:
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nitric acid : HNO3
tellurium : Te
Class:
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elem=Te
redox
Summary:
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Tellurium slowly dissolves in nitric acid.
Description:
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Add a small piece of tellurium to some nitric acid (appr. 52% by weight): The
solid very slowly dissolves. The air above the nitric acid becomes light brown.
The liquid itself becomes green and remains clear.
Heat the liquid with the piece of tellurium: The tellurium now dissolves much
faster. A gas is evolved at the tellurium and the air above the acid now
becomes dark brown.
Let cool down: Almost all tellurium has dissolved, the liquid is light green
and the air above the liquid remains light brown.
Dilute with water approximately 4 times: It looks as if the liquid becomes
turbid and white, but almost immediately this disappears again. The liquid
becomes colorless and clear.