Variable oxidation states Flashcards
What is the oxidation state of Vanadium in V²⁺ ?
+2
What colour is the V²⁺ ion?
violet
What is the oxidation state of vanadium in V³⁺?
+3
What is the colour of the V³⁺ ion?
Green
What is the oxidation state of vanadium in VO²⁺?
+4
What is the colour of the VO²⁺ ion?
Blue
What is the oxidation state of vanadium in VO₂⁺?
+5
What is the colour of the VO₂⁺ ion?
Yellow
What is the first equation when vanadium (V) is reduced by zinc metal in an acidic solution?
2VO₂⁺ + Zn + 4H+ -> 2VO²⁺ + Zn²⁺ + 2H2O
What is the colour change when VO₂⁺ is reduced to VO²⁺?
Yellow to blue
What is the second equation when VO²⁺ is reduced to V³⁺?
2VO²⁺ + Zn + 4H+ -> 2V³⁺ + Zn²⁺ + 2H2O
What is the colour change when VO²⁺ is reduced to V³⁺?
Blue to green
What is the third equation when V³⁺ is reduced to V²⁺?
2V³⁺ + Zn -> 2V²⁺ +Zn²⁺
What is the colour change when V³⁺ is reduced to V²⁺?
green to violet
What is the redox potential?
How easily an atom is reduced to a lower oxidation state
The more positive the redox potential…
…the less stable the ion will be and so the more likely it is to be reduced
What two things affect redox potential?
Ligands
pH
How do ligands affect redox potential?
Different ligands may make the redox potential larger or smaller, depending on how well they bind to the metal ion in a particular oxidation state
How does pH affect the redox potential?
- Some ions need H+ ions to be present in order to be reduced
- Others release OH- ions into solution when they are reduced
Why is Tollen’s reagent used as an oxidising agent to test for aldehydes?
Ag+ is easily reduced to silver metal
