Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
EDTA tetra sodium : (NaOOC CH2)2 N CH2 CH2 N (CH2 COONa)2
ascorbic acid : C6H8O6
sulphuric acid : H2SO4
sodium hydroxide : NaOH
vanadium pentoxide : V2O5
Class:
------
elem=V
coordination
redox
Summary:
--------
Vanadium (IV) does not build complexes with EDTA in acidic environments.
Description:
------------
Dissolve some V2O5 in a solution of NaOH and add an excess amount of sulfuric
acid: The liquid becomes yellow, formation of pervanadyl ([VO2]+).
Add an excess amount of ascorbic acid: The liquid immediately becomes blue
(vanadyl, [VO]2+) and it remains clear. The reaction is fast and complete.
Add some EDTA Na4: The solid dissolves and the liquid remains blue. No
intensification of the color can be observed, nor a shift of color.
Apparently EDTA does not build a coordination complex with vanadyl (at least
not in strongly acidic environments) or the complex has the same color as
free aqueous vanadyl.