Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
hydrogen peroxide : H2O2
hydrochloric acid : HCl
EDTA tetra sodium : (NaOOC CH2)2 N CH2 CH2 N (CH2 COONa)2
zinc : Zn
vanadyl sulfate : VOSO4.5H2O
Class:
------
elem=V
coordination
redox
Summary:
--------
Vanadium (III) apparently builds a coordination complex with EDTA in
strongly acidic environments. This complex is brown.
Description:
------------
Add some zinc to an acidic solution of vanadyl sulfate: The liquid becomes
dark green. On longer standing it becomes lavender, but when it has been
standing in contact with air, it finally becomes green again, when all zinc
is dissolved.
Add an excess amount of EDTA Na4: The solid dissolves and the liquid becomes
brown. It remains clear.
Add much more acid (in the form of HCl, 10% by weight): The liquid remains
brown.
Add two drops of H2O2 (3% by weight): The liquid becomes pale blue, the
vanadium (III) is oxidized to vanadium (IV), resulting in destruction of
the brown coordination complex.