Description of experiment
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Needed compounds:
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sodium persulfate : Na2S2O8
sulphuric acid : H2SO4
vanadyl sulfate : VOSO4.5H2O
Class:
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elem=V
redox
Summary:
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Vanadium (IV) as vanadyl cations, is oxidized by persulfate to vanadium (V)
as pervanadyl.
Description:
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Add some solid sodium peroxosulfate to a slightly acidic solution of vanadyl
sulfate: The sodium peroxosulfate dissolves. The liquid remains clear and
blue.
Heat until the liquid boils: Initially the liquid remains blue, but after a
few seconds it turns darker and the color gradually changes as follows:
sky blue --> darker blue --> dark green --> light green --> green/yellow -->
yellow. The final color is yellow. The whole change takes a few tens of
seconds.
The blue [VO]2+ is oxidized to the yellow [VO2]+.