Chapter 7 Electrochemistry 7 9 Electrode potential and

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Chapter 7 Electrochemistry § 7. 9 Electrode potential and electromotive forces 1. 229 /V

Chapter 7 Electrochemistry § 7. 9 Electrode potential and electromotive forces 1. 229 /V O 2 0. 401 H 2 O 0. 000 H 2 0 2 4 6 -0. 828 8 10 12 14 p. H

7. 9. 1. Influential factors for electrode potential 1) emf’s and G of reaction

7. 9. 1. Influential factors for electrode potential 1) emf’s and G of reaction in different forms Exercise: Compare G 1, G 2, G 3 and E 1, E 2, E 3. reaction: H 2 + Cu 2+ Cu + 2 H+ G 1, E 1 1/2 H 2 + 1/2 Cu 2+ 1/2 Cu + H+ G 2, E 2 Cu + 2 H+ H 2 + Cu 2+ G 3, E 3

2) of electric couple between different oxidation state Give the relationship between Fe 3+

2) of electric couple between different oxidation state Give the relationship between Fe 3+ Exercise Fe 2+ Fe

3) of different electrode Ag. Cl = Ag+ + Cl. Ag(s)|Ag. NO 3(c 1)

3) of different electrode Ag. Cl = Ag+ + Cl. Ag(s)|Ag. NO 3(c 1) ||KCl(c 2) |Ag. Cl(s)|Ag(s) Exercise: deduce the relationship between and

7. 9. 2. Concentration-dependence of Nernst equation for Ag+/Ag electrode (Ag+/Ag) depends on [Ag+]

7. 9. 2. Concentration-dependence of Nernst equation for Ag+/Ag electrode (Ag+/Ag) depends on [Ag+] , or (Ag+/Ag) responds to [Ag+]. The relationship between (Ag+/Ag) and [Ag+] can be used for quantitative electroanalysis of Ag+.

Can we use hydrogen electrode for measuring the p. H of the solution? Give

Can we use hydrogen electrode for measuring the p. H of the solution? Give the principle of the measurement.

7. 9. 3. p. H-dependence of : Pourbaix diagram For electrode reaction with H+

7. 9. 3. p. H-dependence of : Pourbaix diagram For electrode reaction with H+ or OH- participating in, the electrode potential will depend on p. H. = ⊖ + 0. 05916 lga. H+ = 0. 000 - 0. 05916 p. H 1. 229 O 2 /V 2 H+ + 2 e- H 2 O 0. 000 O 2 + 4 H+ + 4 e- 2 H 2 O H 2 0. 401 -0. 828 = ⊖ + 0. 05916 lga. H+ = 1. 229 - 0. 05916 p. H 0 2 4 6 8 10 12 14 p. H-potential diagram/Pourbaix diagram

/V Application of Pourbaix diagram Cu 2+ Cu(OH)2 Cu. O 22 Cu 2

/V Application of Pourbaix diagram Cu 2+ Cu(OH)2 Cu. O 22 Cu 2 O Cu 0 2 4 6 8 10 12 14 p. H

Pourbaix diagram of iron-water system Equilibrium line Fe 3+ Stable zone /V Fe 2

Pourbaix diagram of iron-water system Equilibrium line Fe 3+ Stable zone /V Fe 2 O 3 Stable state Fe 3 O 4 Fe 2+ Fe. O 22 Product Reaction Fe Protection, passivation, active dissolution, 0 2 4 6 8 10 12 14 p. H electroplating, electrosynthesis