1 / 10

The oxidation states of vanadium

The oxidation states of vanadium. Objectives: access multiple oxidation states of V separate compounds via ion exchange chromatography. Vanadium Complexes in This Lab. [V(H 2 O)] 6 2+ [V(H 2 O) 6 ] 3+ [V(H 2 O) 5 O] 2+ [V(OH)O 3 ] 2- Draw 3D structure Give oxidation number of V.

tekli
Download Presentation

The oxidation states of vanadium

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The oxidation states of vanadium Objectives: access multiple oxidation states of V separate compounds via ion exchange chromatography

  2. Vanadium Complexes in This Lab • [V(H2O)]62+ • [V(H2O)6]3+ • [V(H2O)5O]2+ • [V(OH)O3]2- • Draw 3D structure • Give oxidation number of V

  3. Hydrated Vanadium Complexes

  4. 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!

  5. Standard reduction potentials (half reactions, acid) 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

  6. Two couples are needed for determining potential Reaction E0 (V) 5+ → 4+ VO3ˉ + 4H+ + eˉ  VO2+ + 2H2O +1.00 4+ → 3+ VO2+ + 2H+ + eˉ V3+(aq) + H2O +0.34 3+ → 2+ V3+(aq) + eˉ V2+(aq) -0.26 Cl2 + 2eˉ 2Clˉ +1.36 Zn2+ + 2eˉ Zn(Hg) -0.76

  7. Redox chemistry of vanadium (Latimer) • Values for acidic solution (pH = 0) • DG0 = -nFE0 n = mol e- F = 96,500 C / mol e- E0 = standard reduction potential in V (1M conc, 1 atm pressure) 1 Joule = (1 Volt)(1 Coulomb)

  8. Oxidation of vanadium • Oxidizing agent: KMnO4 MnO4- + 8H+ + 5e- ------> Mn2+ + 4 H2O 1.52 V Why is KMnO4a good oxidizing agent? --show oxidations with KMnO4 stepwise

  9. Separation of ions • Ion exchange chromatography • SO32- ions attached to column • Positive ions travel more slowly through column • Can adjust rate via competitive binding resin • Resin must be kept wet to avoid cracking • Resin must have sufficient height to achieve separation • Unsettled height is ~3X greater than settled height

More Related