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Redox reactions

Redox reactions. 2Fe 3+ + Sn 2+  2Fe 2+ + Sn 4+. half-reactions:. Reduction 2Fe 3+ + 2e -  2Fe 2+ oxidation Sn 2+  Sn 4+ + 2e -. Redox reactions. occurring in 1) solution 2) electrochemical cell. 2Fe 3+ + Sn 2+  2Fe 2+ + Sn 4+. Electrochemical Reactions.

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Redox reactions

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  1. Redoxreactions 2Fe3+ + Sn2+ 2Fe2+ + Sn4+ half-reactions: Reduction 2Fe3+ + 2e- 2Fe2+ oxidation Sn2+ Sn4+ + 2e- http:\asadipour.kmu.ac.ir 34 slides

  2. Redoxreactions occurring in 1) solution 2) electrochemical cell. 2Fe3+ + Sn2+ 2Fe2+ + Sn4+ http:\asadipour.kmu.ac.ir 34 slides

  3. Electrochemical Reactions 1)chemical  electric: primary cell (Galvanic cell) 2)electric  chemical: electrolytic cell http:\asadipour.kmu.ac.ir 34 slides

  4. Standard Reduction Potentials Reduction Half-Reaction E(V) F2(g) + 2e- 2F-(aq) 2.87 Au3+(aq) + 3e- Au(s) 1.50 Cl2(g) + 2 e- 2Cl-(aq) 1.36 Cr2O72-(aq) + 14H+(aq) + 6e- 2Cr3+(aq) + 7H2O 1.33 O2(g) + 4H+ + 4e- 2H2O(l) 1.23 Ag+(aq) + e- Ag(s) 0.80 Fe3+(aq) + e- Fe2+(aq) 0.77 Cu2+(aq) + 2e- Cu(s) 0.34 Sn4+(aq) + 2e- Sn2+(aq) 0.15 2H+(aq) + 2e- H2(g) 0.00 Sn2+(aq) + 2e- Sn(s) -0.14 Ni2+(aq) + 2e- Ni(s) -0.23 Fe2+(aq) + 2e- Fe(s) -0.44 Zn2+(aq) + 2e- Zn(s) -0.76 Al3+(aq) + 3e- Al(s) -1.66 Mg2+(aq) + 2e- Mg(s) -2.37 Li+(aq) + e- Li(s) -3.04 Ox. agent strength increases Red. agent strength increases http:\asadipour.kmu.ac.ir 34 slides

  5. Balancing of redox reactions.Under Acidic conditions 1. Identify oxidized and reduced species Write the half reaction for each. 2. Balance the half rxn separately except H & O’s. Balance: Oxygen by H2O Balance: Hydrogen by H+ Balance: Charge by e - 3. Multiply each half reaction by a coefficient. There should be the same # of e- in both half-rxn. 4. Add the half-rxn together, the e - should cancel. http:\asadipour.kmu.ac.ir 34 slides

  6. Balancing of redox reactions.Under Basic conditions 1. Identify oxidized and reduced species Write the half reaction for each. 2. Balance the half rxn separately except H & O’s. Balance: Oxygen by H2O Balance: Hydrogen by OH- Balance: Charge by e - 3. Multiply each half reaction by a coefficient. There should be the same # of e- in both half-rxn. 4. Add the half-rxn together, the e - should cancel. http:\asadipour.kmu.ac.ir 34 slides

  7. Balancing of redox reactions H2O2 (aq) + Cr2O7-2(aq )  Cr 3+ (aq) + O2 (g) Redox reaction ====================================== 1)write 2 half reactions Half Rxn (red): Cr2O7-2 (aq)  Cr3+ Half Rxn (oxid): H2O2 (aq) O2 2)Atom balance Cr2O7-2 (aq) 2Cr3+ H2O2 (aq) O2 http:\asadipour.kmu.ac.ir 34 slides

  8. Balancing of redox reactions 3)Oxygen balance Half Rxn (red): Cr2O7-2 (aq)  2Cr3+ + 7 H2O Half Rxn (oxi): H2O2 (aq) O2 4)Hydrogen balance Half Rxn (red): 14H++ Cr2O7-2 (aq)  2Cr3+ + 7 H2O Half Rxn (oxi): H2O2 (aq) O2 + 2H+ 5)Electron balance 6e- + 14H+ + Cr2O7-2 (aq)  2Cr3+ + 7 H2O H2O2 (aq) O2 + 2H+ + 2e- http:\asadipour.kmu.ac.ir 34 slides

  9. Balancing of redox reactions 6) Equalize of produced and consumed electrons 6e- + 14H+ + Cr2O7-2 (aq)  2Cr3+ + 7 H2O ( H2O2 (aq) O2 + 2H+ + 2e- ) x 3 7)Multiply each half reaction 8 H+ + 3H2O2 + Cr2O72- 2Cr+3 + 3O2+ 7H2O http:\asadipour.kmu.ac.ir 34 slides

  10. Balance the redox reactions H+ I2 +S2O32-⇋ I- +S4O62- I2 +S2O32-⇋ I- +SO42- OH- http:\asadipour.kmu.ac.ir 34 slides

  11. Redox titration 2Ag+ +Cu(S) 2Ag(s) +Cu2+ Redox reaction --------------------------------------------------------------------- Cu│Cu2+ (xM) ││ Ag+(yM) │ Ag Cu2+ + 2e- Cu(S) Eo=0.337 Ag+ + e- Ag(s) Eo=0.799 http:\asadipour.kmu.ac.ir 34 slides

  12. Redox titration 2Ag+ +Cu(S) 2Ag(s) +Cu2+ RedoxEo =0.462 ECell=Ecathod-Eanod=EAg-ECu ECell=0 → EAg =ECuدرتعادل http:\asadipour.kmu.ac.ir 34 slides

  13. Keq EAg = ECu http:\asadipour.kmu.ac.ir 34 slides

  14. Keq • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • MnO4-+5e-+8H+→ Mn2++ 4H20 E0=1.51 n=5 • 5Fe2 +→ 5Fe3++5e E0= -0.771 n=1 http:\asadipour.kmu.ac.ir 34 slides

  15. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M (1M H2SO4) • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe3+ + e Fe2+ E0=0.771 5ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  16. Attention 1!!!!!! • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe2+Fe3+ + eE0=-0.771 5ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  17. Attention 2!!!!!! • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • 5Fe2+5Fe3+ + 5eE0=-0.771 5ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  18. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe3+ + e Fe2+ E0=0.771 10 ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  19. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe3+ + e Fe2+ E0=0.771 15 ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  20. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe3+ + e Fe2+ E0=0.771 19 ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  21. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe3+ + e Fe2+ E0=0.771 19.5 ml Before Eq http:\asadipour.kmu.ac.ir 34 slides

  22. Titration curve • 1e+Fe3+  Fe2+ 5+MnO4-+8H+  Mn2+ 20 ml At Eq ×5 http:\asadipour.kmu.ac.ir 34 slides

  23. Titration curve 5X Y 5Y X MnO4-+5Fe2++8H+ Mn2++5Fe3++4H20 /6 http:\asadipour.kmu.ac.ir 34 slides

  24. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Fe3+  Fe2+ • Mno4-+8H+  Mn2+ 20 ml At Eq http:\asadipour.kmu.ac.ir 34 slides

  25. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Mno4-+8H+  Mn2+ 20.5 ml After Eq http:\asadipour.kmu.ac.ir 34 slides

  26. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Mno4-+8H+  Mn2+ 21 ml After Eq http:\asadipour.kmu.ac.ir 34 slides

  27. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Mno4-+8H+  Mn2+ 22 ml After Eq http:\asadipour.kmu.ac.ir 34 slides

  28. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Mno4-+8H+  Mn2+ 23 ml After Eq http:\asadipour.kmu.ac.ir 34 slides

  29. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Mno4-+8H+  Mn2+ 25 ml After Eq http:\asadipour.kmu.ac.ir 34 slides

  30. Titration curve • 100 ml Fe2+ 0.5 M WITH Mno4- 0.5 M • MnO4-+5Fe2++8H+  Mn2++5Fe3++4H20 • Mno4-+8H+  Mn2+ 30 ml After Eq http:\asadipour.kmu.ac.ir 34 slides

  31. Titration curve http:\asadipour.kmu.ac.ir 34 slides

  32. Titration curve data Height is related to Keq Not related to concentration http:\asadipour.kmu.ac.ir 34 slides

  33. Titration curve http:\asadipour.kmu.ac.ir 34 slides

  34. Titration curve http:\asadipour.kmu.ac.ir 34 slides

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