oxidation states of vanadium
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Oxidation states of vanadium. AH Chemistry, Unit 1(c). Aims. Illustrate the presence of several oxidation states for vanadium Show how it is possible to change from one oxidation state to another. What are “oxidation states”?. - PowerPoint PPT PresentationTRANSCRIPT
Oxidation states of vanadiumAH Chemistry, Unit 1(c)
Aims
• Illustrate the presence of several oxidation states for vanadium
• Show how it is possible to change from one oxidation state to another
What are “oxidation states”?• The actual charge of an atom if the
atom is a monatomic ion, or the hypothetical charge assigned to an atom by certain rules
Rules1. Elements are 02. Atoms of monatomic ions have charge
of ion3. O is -2 in most compounds4. H is +1 in most compounds5. F is -1 in all compounds6. Sum of numbers in a compound is 0;
in a polyatomic ion is charge of ion
Example• Oxidation number of Cl in:
– HClO4 (perchloric acid)
– ClO3- (chlorate ion)
The significance of transition metals• Transition metals exhibit variable oxidation
states of differing stability• A change in oxidation state can bring about a
change in colour
Oxidation and reduction• Oxidation can be considered as an increase
in oxidation number
• Reduction can be considered as a decrease in oxidation number
• Compounds with metals in a high oxidation state tend to be oxidising agents whereas compounds with metals in a low oxidation state are often reducing agents
Oxidation states of vanadium
Ion (hydrated)
VO2+ VO2+ V3+ V2+
Colour Yellow Blue Green Violet
Oxidation state
5 4 3 2
Name Dioxovanadium(V) Oxovanadium(IV) Vanadium(III) Vanadium(II)
Summary of results
Test ObservationsSummary of
reaction
Ammonium vandate + acid
White solid turned red and dissolved to a yellow solution
VO3- VO2
+
(+5) (+5)
Summary of results
Test ObservationsSummary of
reaction
Vanadium(V) + zinc The zinc effervesced and the yellow solution became green, blue, green again and, eventually, violet
VO2+ VO2+ V3+ V2+
(+5) (+4) (+3) (+2)
Summary of results
Test ObservationsSummary of
reaction
Vanadium(II) + manganate(VII)
The violet solution became green, blue, green-yellow and, finally, pink
V2+ V3+ VO2+ VO2+
(+2) (+3) (+4) (+5)
Summary of results
Test ObservationsSummary of
reaction
Vanadium(V) + sulphite. Add vanadium(II)
The yellow solution became blue. On adding vanadium(II) the mixture became green
VO2+ VO2+
(+5) (+4)
VO2+ + V2+ V3+
(+4) + (+2) (+3)
Summary of results
Test ObservationsSummary of
reaction
Vanadium(V) + iodide + thiosulphate
The yellow solution became a muddy brown. Addition of thiosulphate gave a clear blue solution
VO2+ VO2+
(+5) (+4)