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The Oxidation States of Vanadium

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Separate compounds via ion exchange chromatography. Vanadium Complexes ... 4 3 Hg/Zn amalgam. 3 2 Hg/Zn amalgam. Reaction with amalgam may occur faster than ... – PowerPoint PPT presentation

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Title: The Oxidation States of Vanadium


1
The Oxidation States of Vanadium
  • Objectives
  • Access multiple oxidation states of vanadium
  • Separate compounds via ion exchange chromatography

2
(No Transcript)
3
Vanadium Complexes in This Lab
  • V(H2O)62
  • V(H2O)63
  • V(H2O)5O2
  • V(OH)O32-

4
Hydrated Vanadium Complexes
5
Reduction of Vanadium
  • 5 ? 4 HCl (done in hood!)
  • 4 ? 3 Hg/Zn amalgam
  • 3 ? 2 Hg/Zn amalgam
  • Reaction with amalgam may occur faster than
  • expected do not overdo shaking!

6
Standard Reduction Potentials
  • Reaction E0 (V)
  • 5?4 VO3- 4H e- ? VO2 2H2O 1.00
  • 4?3 VO2 2H e- ? V3(aq) H2O 0.34
  • 3?2 V3(aq) e- ? V2(aq) -0.26

7
Two Couples Are Needed For Determining Potential
Reaction E0 (V) 5 ? 4 VO3 4H e ?
VO2 2H2O 1.00 4 ? 3 VO2 2H e ?
V3(aq) H2O 0.34 3 ? 2 V3(aq) e ?
V2(aq) -0.26 Cl2 2e ? 2Cl 1.36 Z
n2 2e ? Zn(Hg) -0.76
8
Separation of ions
  • Ion exchange chromatography
  • SO32- ions attached to column
  • Most highly positively charged ions travel more
    slowly through column

resin
  • Can adjust rate via competitive binding
  • Resin must be kept wet to avoid cracking
  • Resin must have sufficient height to achieve
    separation
  • Unsettled height is 3X greater than settled
    height

9
Oxidation of Vanadium
  • Oxidizing agent KMnO4
  • MnO4- 8H 5e- ------gt Mn2 4 H2O 1.52 V
  • Why is KMnO4 a good oxidizing agent?

--show oxidations with KMnO4 stepwise
10
Summary
--Synthesize vanadium compounds in four
different oxidation states
--Separate products by ion exchange
chromatography
--Determine concentrations of vanadium compounds
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