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.

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

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

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

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) H + (aq) + 2e -  H 2 (g) 0.00 Sn 2+ (aq) + 2e -  Sn(s) Ni 2+ (aq) + 2e -  Ni(s) Fe 2+ (aq) + 2e -  Fe(s) Zn 2+ (aq) + 2e -  Zn(s) Al 3+ (aq) + 3e -  Al(s) Mg 2+ (aq) + 2e -  Mg(s) Li + (aq) + e -  Li(s) Ox. agent strength increases Red. agent strength increases http:\asadipour.kmu.ac.ir 34 slides

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

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

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

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

Balancing of redox reactions 6) Equalize of produced and consumed electrons 6e H + + Cr 2 O 7 -2 (aq)  2Cr 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 O 2 + 7H 2 O http:\asadipour.kmu.ac.ir 34 slides

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 http:\asadipour.kmu.ac.ir 34 slides H+H+ OH -

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

Redox titration E Cell =0 → E Ag =E Cu درتعادل http:\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

K eq slides E Ag = E Cu

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

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

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

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

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

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

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

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

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

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

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

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

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

Titration curve 100 ml Fe M WITH Mno M MnO Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno H +  Mn ml After Eq slides

Titration curve 100 ml Fe M WITH Mno M MnO Fe 2+ +8H +  Mn 2+ +5Fe 3+ +4H 2 0 Mno H +  Mn ml After Eq slides

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

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

Titration curve http:\asadipour.kmu.ac.ir 34 slides ml of MnO4K E(v) Δ E/ Δ V Δ2 E/ Δ V

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

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

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