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SS5.1 Investigating the oxidation states of Vanadium
Ammonium vanadate dissolves in moderately concentrated acid to give a yellow solution, the ion present being of oxidation state +5. Granuled zinc is added to act as a reducing agent and the oxidation state of the vanadium changes from +5 to +4 to +3 to +2 with the corresponding colour changes from yellow to blue to green to violet.
This video demonstrates the coloured nature of transition metals in addition to demonstrating that the actual colour depends on the oxidation state.
Left click to see high quality video clip, right click to download (6.5MB)
For further information see Salters Advanced Chemistry, 2000, Activities and Assessment Pack, Second Edition, ISBN 0 435 631217