Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydrogen peroxide : H2O2
sodium dithionite : Na2S2O4 . 2H2O
ammonium molybdate : (NH4)6Mo7O24 . 4H2O
Class:
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elem=Mo
redox
Summary:
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When molybdates are reduced, then intense blue compounds are formed. It
is believed that these intensely coloured compounds are multi-nuclear
Mo-compounds, with different nuclei having different oxidation states.
Description:
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Add a little quantity of solid sodium dithionite to a solution of
ammonium molybdate: The solid dissolves and the liquid turns dark
green/blue.
Add an excess amount of H2O2 (3% by weight): The liquid turns pale yellow.
Add an excess amount of sodium dithionite: Formation of a brown compound
near the crystals of sodium dithionite. A little further from the crystals,
the brown compound changes to a dark blue/green compound. There also is
a smell of hydrogen sulfide and sulphur dioxide.