Description of experiment
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Needed compounds:
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nitric acid : HNO3
sodium hypophosphite : NaH2PO2
sodium orthovanadate : Na3VO4
Class:
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elem=P,V
redox
Summary:
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Vanadium(V) in acidic solution is reduced by hypophosphite to vanadium(IV), but
there is no further reduction to a lower oxidation state.
Description:
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Dissolve some sodium orthovanadate in water: A colorless and clear solution is
obtained.
Add some excess amount of dilute nitric acid: The liquid turns yellow and
remains clear.
Add some solid sodium hypophosphite: The solid fairly easily dissolves and the
liquid remains yellow.
Heat the liquid until it starts boiling: The color shifts from yellow to blue,
through different shades of green.
Keep on heating and allow to boil gently: No further change of color. The
liquid remains skyblue. This is the color of vanadyl ion, VO(2+).