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Chapter 7 Electrochemistry

1.229. O 2.  / V. 0.401. H 2 O. 0.000. H 2. -0.828. 0. 2. 4. 6. 8. 12. 14. pH. 10. Chapter 7 Electrochemistry. §7.9 Electrode potential and electromotive forces. 7.9.1. Influential factors for electrode potential. 1) emf’s and  r G m of a reaction in different forms.

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Chapter 7 Electrochemistry

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  1. 1.229 O2  / V 0.401 H2O 0.000 H2 -0.828 0 2 4 6 8 12 14 pH 10 Chapter 7 Electrochemistry §7.9 Electrode potential and electromotive forces

  2. 7.9.1. Influential factors for electrode potential 1) emf’s and rGm of a reaction in different forms Exercise: Compare G1, G2, G3 and E1, E2, E3. reaction: H2 + Cu2+ Cu + 2H+G1, E1 1/2 H2 + 1/2 Cu2+ 1/2 Cu + H+ G2, E2 Cu + 2H+ H2 + Cu2+G3, E3

  3. Fe Fe2+ Fe3+ 2)  between different oxidation states Give the relationship between  Initial state and final state Exercise

  4. Exercise: deduce the relationship between and 3) of relevant electrodes AgCl = Ag+ + Cl- Ag(s)|AgNO3(c1) ||KCl(c2) |AgCl(s)|Ag(s)

  5. 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 quantitativeelectroanalysis of Ag+.

  6. Can we use hydrogen electrode for measuring the pH of the solution? Give the principle of the measurement. Normal and italic Exercise: why electrode Hg(l)Hg2SO4(s)CaSO4(s)Ca2+(m) can be used to measure the concentration of Ca2+ in a solution?

  7. 1.229 O2  / V 0.401 H2O 0.000 H2 -0.828 0 2 4 6 8 12 14 pH 10 7.9.3. pH-dependence of : Pourbaix diagram For electrode reaction with H+ or OH- participating in, the electrode potential will depend on pH. 2H+ + 2e- H2  = ⊖ + 0.05916 lgaH+ = 0.000 - 0.05916 pH O2 + 4H+ + 4e- 2H2O  = ⊖ + 0.05916 lgaH+ = 1.229 - 0.05916 pH pH-potential diagram/Pourbaix diagram

  8.  / V Cu2+ Cu(OH)2 CuO22 Cu2O Cu 0 2 4 6 8 12 14 10 pH Application of Pourbaix diagram

  9. Fe3+  / V Fe2O3 Fe3O4 Fe2+ FeO22 Fe 0 2 4 6 8 12 14 10 pH Pourbaix diagram of iron-water system Equilibrium line Stable zone Stable state Product Reaction Protection, passivation, active dissolution, electroplating, electrosynthesis

  10. Group discussion -2 • How can you measure the liquid-liquid junction potential of a HCl/KCl interface? Write out the notation of the cell you use to conduct your measurement. • A potential is usually established across the cell membrane due to the concentration difference of K+ inside and outside a cell, which is named as membrane potential. This potential is crucial for sensation of any living thing. Can you design an experimental apparatus for measuring the membrane potential of a cell? State the principle you use.

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