Schedule Today (4/10): Chapter 11 Friday (4/12): Chapter 11 Should have finished reading Chapter 11 Friday (4/12): Chapter 11 Be ready with any questions Monday (4/15): Chapter 21 Start reading Chapter 21 No office hours Monday, April 15

Concentration Cells Note the electrodes.

Concentration Cells – Ksp 1.0M NaCl and 1.0M Ag+(aq) excess AgCl(s)

Clicker Question a) 0.54 V b) 0.83 V c) 0.97 V d) 1.23 V e) 1.52 V Ni 0.0010 M Ni2+ 1.0 M HCl Ag AgCl(s) 1.0 M HCl Determine Ɛ for this cell. Ksp for AgCl = 1.6 x 10–10 Ni2+ + 2e–  Ni –0.23 V Ag+ + e–  Ag 0.80 V a) 0.54 V b) 0.83 V c) 0.97 V d) 1.23 V e) 1.52 V

Batteries

Corrosion 0.44 V 0.40 V Blue from KFe[Fe(CN)6]•H2O Pink from OH– and phenolphthalein

Prevention of Corrosion Find a metal more reactive than Fe (a “sacrificial metal”). Fe  Fe2+ + 2e– (0.44 V) Mg  Mg2+ + 2e– (2.37 V) Zn  Zn2+ + 2e– (0.76 V)

Galvanic vs. Electrolytic Naturally occurs to reduce Cu2+ and oxidize Zn. But what if we want to form Zn? Zn2+ + 2e–  Zn (–0.76 V) Cu2+ + 2e–  Cu (0.34 V)

Electroplating Get silver metal from dissolved silver ions. To reduce silver ions, an oxidation must occur. Ag+ + e–  Ag (0.80 V)