Transition Metals Part 2 Flashcards
How many common oxidationstates does vanadium have
4
When can the different oxidation states of vanadium be seen
When a solution of ammonium vanadate is reduced using zinc in acidic conditions
Common oxidation states of vanadium: what colour is VO2 + ion with ON +5
Yellow
Common oxidation states of vanadium: what colour is ion VO2+ with ON +4
Blue
Common oxidation states of vanadium: what colour is V3+ ion with ON +3
Green
Common oxidation states of vanadium: what colour is V2+ ion with ON +2
Violet
Half equation reduction VO2 + to VO2+
VO2 + 2H+ + e- > VO2+ + H2O
Half equation oxidation of Zn
Zn > Zn2+ + 2e-
Overall equation reduction of VO2 + to VO2+ by zinc in acidic conditions
2VO2 + + 4H+ + Xn> 2VO2+ + 2H2O + Zn2+
Half equation for reduction of VO2+ to V3+
VO2+ + 2H+ + e- > V3+ + H2O
Half equation for oxidation of Zn
Zn > Zn2+ + 2e-
Overall equation for reduction of VO2+ to V3+ in acidic conditions
2VO2+ + 4H+ + Zn > 2V3+ + Zn2+ + 2H2O
Half equation for reduction of V3+ to V2+
V3+ + e- > V2+
Half equation for oxidation of Zn
Zn > Zn2+ + 2e-
Overall equation for reduction of V3+ to V2+ by zinc in acidic conditions
2V3+ + Zn > 2V2+ + Zn2+
Formula for tollens reagent
[Ag(NH3)2]+
What happens to an aldehyde when it’s warmed with tollens reagent
It’s oxidised to a carboxylic acid
What happens to the silver ions when tollens is reacted with an aldehyde
Silver ions reduced to silver metal
Equation for reduction of tollens reagent
[Ag(NH3)2]+ + e- > Ag + 2NH3
Why do ketones give no reaction in tollens test
Can’t be oxidised
What is the redox potential of an ion/atom a measure of
How easily it is reduced to a lower oxidation state.
Why does a more positive redox potential mean an ion is less stable
More likely to be reduced
What is the redox potential the same as standard electrode potential providing
It is measured unde standard conditions in aqueous solution
Why are the ligands surrounding the metal ion water in standard electrode potential
Standard electrode potentials are measured in aqueous solution
Why will changing the ligand change the value of the redox potential
Other ligands will bond more or less strongly to central mental ion
Half equation for reduction of dichromate in acidic conditions
Cr2O72- + 14H+ > 6e- > 2Cr3+ + 2H2O
What effect would reducing pH of dichromate have on redox potential
Lower pH > higher [H+] > eqm RHS > more +ve redox potential
Half Equation for reduction of manganate
MnO4- + 8H+ + 5e- > Mn2+ + 4H2O
