1. Previously in Chem104: It’s not all about Batteries: The Great Cycle of Energy Not at Standard? Membrane Potentials Today in Chem104: Electron Transfer Concepts overview Why we need electrochemical cells Cell notation conventions

2. Electron Transfer Reactions: The BIG PICTURE Major Concepts and Equations 2. The Thermodynamic view:  G = -n F E rxn But only at 1.0 M and 25 deg C And DON’T multiply by coefficients! At any other concentration or temperature: E rxn = E o rxn – (RT/nF) ln Q 1. E rxn = E red + E ox but also: ln K= (nF/RT) E o rxn 3. A corollary from the Thermodynamic view: The more positive the potential (E o rxn, E o red, E o ox ) the more thermodynamically favored it is.

3. Why we need Electrochemical Cells (First a demo...) To convert Energy to (useful) Work How does a cell do that? Separate the two half reactions To convert electron transfer (movement) to an electrical current

4. Electrochemical Cells: how do we make them?

5. Cell Notation Reaction: Cu o + 2 Ag +  Cu 2+ + 2 Ag o Cell notation: Cu | Cu 2+ || Ag + | Ag o E- flow anodecathode

6. What will happen for this cell? Cu o + Fe 3+  Cu 2+ + Fe o reagents products

7. TABLE OF STANDARD REDUCTION POTENTIALS E o (V) Cu 2+ + 2e-  Cu+0.34 I2I2 + 2e-  2 I-+0.53 Zn 2+ + 2e-  Zn-0.76 stronger reducing ability Ag + + e-  Ag+0.80 Fe 3+ + e-  Fe+0.77 2+ Pb 2+ + 2e-  Pb-0.13 Fe 3+ + 3e-  Fe-0.04 Al 3+ + 3e-  Al-1.66Na + + e-  Na+2.71 K + + e-  K+2.93 2 H + + 2e-  H 2 0.00 stronger oxidizing ability

8. What will happen for this cell? Cu o + Fe 3+  Cu 2+ + Fe o reagents products

9. Electrochemical Cells: terms to know Cells that do Spontaneous Electron Transfer: Galvanic or Voltaic Cells for Non-Spontaneous Electron Transfer: Electrolytic *these require another energy source, a battery Cell Components: Anode – where oxidation —anodic rxn—occurs, (-) charged; Cathode – where reduction occurs—cathodic rxn—occurs, (+) charged Cell Potential (EMF): E cell = E cathode - E anode Note difference !!! E rxn = E red + E ox

10. Electrochemical Cells: how do we make them?

11. Electrochemical Cells in your lifeAlkaline Dry Cell

12. Electrochemical Cells in your life Lead –Acid Battery

13. The Great Cycle of Energy GG EK eq  G = -RTlnK  G = -n F E rxn lnK = (nF/RT)E rxn