Description of experiment
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Needed compounds:
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hydrogen peroxide : H2O2
sodium hydroxide : NaOH
EDTA tetra sodium : (NaOOC CH2)2 N CH2 CH2 N (CH2 COONa)2
sulphuric acid : H2SO4
sodium sulfite : Na2SO3
potassium permanganate : KMnO4
Class:
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elem=Mn
redox
coordination
Summary:
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Manganese (II) ions apparently do not form coordination complexes with EDTA.
If they do so, then the coordination complex is (almost) colorless.
Description:
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Prepare a solution, containing Mn2+ ions by reducing potassium permanganate
with a slight excess amount of sodium sulfite in dilute sulfuric acid.
Add some solid EDTA tetra sodium to the acidic solution, containing Mn2+:
The EDTA dissolves, no further visible reaction.
Add some solid NaOH: The solid dissolves, the liquid becomes turbid, first
it is brownish pink, but quickly the color shifts to yellowish brown, due to
oxidation of manganese (II) compounds to manganese (III) or manganese (IV).
Add some H2O2 (3% solution): The liquid remains turbid and becomes dark brown.
Strong evolution of a gas (O2).