2. Redox reactions half-reactions: Reduction 2Fe 3+ + 2e -  2Fe 2+ oxidation Sn 2+  Sn 4+ + 2e - 2Fe 3+ + Sn 2+  2Fe 2+ + Sn 4+ 9203091http:\asadipour.kmu.ac.ir 34 slides

3. Redox reactions occurring in 1) solution 2) electrochemical cell. 2Fe 3+ + Sn 2+  2Fe 2+ + Sn 4+ 9203092http:\asadipour.kmu.ac.ir 34 slides

4. Electrochemical Reactions 1)chemical  electric: primary cell (Galvanic cell) 2)electric  chemical: electrolytic cell 9203093http:\asadipour.kmu.ac.ir 34 slides

5. Standard Reduction Potentials Reduction Half-Reaction E  (V) F 2 (g) + 2e -  2F - (aq) 2.87 Au 3+ (aq) + 3e -  Au(s) 1.50 Cl 2 (g) + 2 e -  2Cl - (aq) 1.36 Cr 2 O 7 2- (aq) + 14H + (aq) + 6e -  2Cr 3+ (aq) + 7H 2 O 1.33 O 2 (g) + 4H + + 4e -  2H 2 O(l) 1.23 Ag + (aq) + e -  Ag(s) 0.80 Fe 3+ (aq) + e -  Fe 2+ (aq) 0.77 Cu 2+ (aq) + 2e -  Cu(s) 0.34 Sn 4+ (aq) + 2e -  Sn 2+ (aq) 0.15 2H + (aq) + 2e -  H 2 (g) 0.00 Sn 2+ (aq) + 2e -  Sn(s) -0.14 Ni 2+ (aq) + 2e -  Ni(s) -0.23 Fe 2+ (aq) + 2e -  Fe(s) -0.44 Zn 2+ (aq) + 2e -  Zn(s) -0.76 Al 3+ (aq) + 3e -  Al(s) -1.66 Mg 2+ (aq) + 2e -  Mg(s) -2.37 Li + (aq) + e -  Li(s) -3.04 Ox. agent strength increases Red. agent strength increases 9203094http:\asadipour.kmu.ac.ir 34 slides

6. 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 H 2 O 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. 9203095http:\asadipour.kmu.ac.ir 34 slides

7. 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 H 2 O 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. 9203096http:\asadipour.kmu.ac.ir 34 slides

8. Balancing of redox reactions H 2 O 2 (aq) + Cr 2 O 7 -2 (aq )  Cr 3+ (aq) + O 2 (g) Redox reaction ====================================== 1)write 2 half reactions Half Rxn (red): Cr 2 O 7 -2 (aq)  Cr 3+ Half Rxn (oxid): H 2 O 2 (aq)  O 2 2)Atom balance Cr 2 O 7 -2 (aq)  2Cr 3+ H 2 O 2 (aq)  O 2 9203097http:\asadipour.kmu.ac.ir 34 slides

9. Balancing of redox reactions 3)Oxygen balance Half Rxn (red): Cr 2 O 7 -2 (aq)  2Cr 3+ + 7 H 2 O Half Rxn (oxi): H 2 O 2 (aq)  O 2 4)Hydrogen balance Half Rxn (red): 14H + + Cr 2 O 7 -2 (aq)  2Cr 3+ + 7 H 2 O Half Rxn (oxi): H 2 O 2 (aq)  O 2 + 2H + 5)Electron balance 6e - + 14H + + Cr 2 O 7 -2 (aq)  2Cr 3+ + 7 H 2 O H 2 O 2 (aq)  O 2 + 2H + + 2e - 9203098http:\asadipour.kmu.ac.ir 34 slides

10. Balancing of redox reactions 6) Equalize of produced and consumed electrons 6e - + 14H + + Cr 2 O 7 -2 (aq)  2Cr 3+ + 7 H 2 O ( H 2 O 2 (aq)  O 2 + 2H + + 2e - ) x 3 7)Multiply each half reaction 8 H + + 3H 2 O 2 + Cr 2 O 7 2-  2Cr +3 + 3O 2 + 7H 2 O 9203099http:\asadipour.kmu.ac.ir 34 slides

11. Balance the redox reactions I 2 +S 2 O 3 2- ⇋ I - +S 4 O 6 2- I 2 +S 2 O 3 2- ⇋ I - +SO 4 2- 92030910http:\asadipour.kmu.ac.ir 34 slides H+H+ OH -

12. Redox titration 2Ag + + Cu (S)  2Ag (s) + Cu 2+ Redox reaction --------------------------------------------------------------------- Cu│Cu 2+ (xM) ││ Ag + (yM) │ Ag Cu 2+ + 2e -  Cu(S) E o =0.337 Ag + + e -  Ag (s) E o =0.799 92030911http:\asadipour.kmu.ac.ir 34 slides

13. Redox titration E Cell =0 → E Ag =E Cu درتعادل 92030912http:\asadipour.kmu.ac.ir 34 slides 2Ag + + Cu (S)  2Ag (s) + Cu 2+ Redox E o =0.462 E Cell =E cathod -E anod =E Ag -E Cu

14. K eq 92030913 http:\asadipour.kmu.ac.ir 34 slides E Ag = E Cu

15. K eq MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 MnO 4 - +5e - +8H + → Mn 2+ + 4H 2 0 E 0 =1.51 n=5 5Fe 2 + → 5Fe 3+ +5e E 0 = -0.771 n=1 92030914http:\asadipour.kmu.ac.ir 34 slides

16. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M (1M H 2 SO 4 ) MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 3+ + e  Fe 2+ E 0 =0.771 5ml Before Eq 92030915http:\asadipour.kmu.ac.ir 34 slides

17. Attention 1!!!!!! 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 2+  Fe 3+ + e E 0 =-0.771 5ml Before Eq 92030916http:\asadipour.kmu.ac.ir 34 slides

18. Attention 2!!!!!! 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 5Fe 2+  5Fe 3+ + 5e E 0 =-0.771 5ml Before Eq 92030917http:\asadipour.kmu.ac.ir 34 slides

19. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 3+ + e  Fe 2+ E 0 =0.771 10 ml Before Eq 92030918http:\asadipour.kmu.ac.ir 34 slides

20. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 3+ + e  Fe 2+ E 0 =0.771 15 ml Before Eq 92030919http:\asadipour.kmu.ac.ir 34 slides

21. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 3+ + e  Fe 2+ E 0 =0.771 19 ml Before Eq 92030920http:\asadipour.kmu.ac.ir 34 slides

22. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 3+ + e  Fe 2+ E 0 =0.771 19.5 ml Before Eq 92030921http:\asadipour.kmu.ac.ir 34 slides

23. Titration curve 1e+Fe 3+  Fe 2+ 5+MnO 4 - +8H +  Mn 2+ 20 ml At Eq 92030922http:\asadipour.kmu.ac.ir 34 slides ×5

24. Titration curve 92030923http:\asadipour.kmu.ac.ir 34 slides MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 /6 5X X Y 5Y

25. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Fe 3+  Fe 2+ Mno 4 - +8H +  Mn 2+ 20 ml At Eq 92030924http:\asadipour.kmu.ac.ir 34 slides

26. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno 4 - +8H +  Mn 2+ 20.5 ml After Eq 92030925http:\asadipour.kmu.ac.ir 34 slides

27. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno 4 - +8H +  Mn 2+ 21 ml After Eq 92030926http:\asadipour.kmu.ac.ir 34 slides

28. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno 4 - +8H +  Mn 2+ 22 ml After Eq 920309 27 http:\asadipour.kmu.ac.ir 34 slides

29. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno 4 - +8H +  Mn 2+ 23 ml After Eq 920309 28 http:\asadipour.kmu.ac.ir 34 slides

30. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno 4 - +8H +  Mn 2+ 25 ml After Eq 92030929http:\asadipour.kmu.ac.ir 34 slides

31. Titration curve 100 ml Fe 2+ 0.5 M WITH Mno 4 - 0.5 M MnO 4 - +5Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno 4 - +8H +  Mn 2+ 30 ml After Eq 92030930http:\asadipour.kmu.ac.ir 34 slides

32. Titration curve 92030931http:\asadipour.kmu.ac.ir 34 slides ml of MnO4K E(v) Δ E/ Δ V Δ2 E/ Δ V2 50.743 100.7710.0056 150.7990.00560 190.8460.011750.001537 19.50.8660.040.0565 201.3871.0422.004 20.51.4910.208-1.668 211.4940.006-0.404 221.4980.004-0.002 231.50.002-0.002 251.5030.0015-0.00025 301.5040.0002-0.00026

33. Titration curve data 92030932http:\asadipour.kmu.ac.ir 34 slides Height is related to K eq Not related to concentration

34. Titration curve 92030933http:\asadipour.kmu.ac.ir 34 slides

35. Titration curve 92030934http:\asadipour.kmu.ac.ir 34 slides