Variable Oxidation States (Booklet 2) Flashcards
What can cause changes to the colour of complexes ?
changes to oxidation state
What is the colour of VO+2
YOU BETTER GET VANADIUM
+5 + 4 +3 +2
YELLOW
What is the colour of VO-3 ?
YELLOW
What is the colour of VO2+ ?
BLUE
What is the colour of V3+ ?
Green
What is the colour of V2+ ?
Violet
Vanadium has 4 major oxidation states what are they ?
+2, +3, +4, and +5
What does a redox titration involve ?
an oxidising agent can be titrated against a reducing agent
What is the procedure for a redox titration of iron (II) with manganate (VII)
Purple KMNO4 solution is added from a burette to a solution of Fe2+ ions, acidifed with H2SO4
Purple colour disappears as MnO-4 ions are converted to pink Mn2+ ions to leave virtually colourless solution.
An extra drop MnO-4 turns the solution pink/purple as MnO-4 is in XS ( this is the equivalence point)
What is Manganate (VII) ?
a very strong oxidising agent
Why is an indicator not needed in a redox titration with KMNO-4
The transition metal changes colour as it changes oxidation state so an indicator is not needed
IT IS SELF INDICATING
Some catalysts work by by chemisorption. Explain this process
reactant molecules are absorbed into active sites on the surface of the catalyst
the bonds in the reactant molecules are weakened and this holds the reactant molecules closer together on the metal surface
How do impurities poison a catalyst ?
they block active sites
