CHAPTER 6: FIGURE 6B.2 PHYSICAL CHEMISTRY: THERMODYNAMICS, STRUCTURE, AND CHANGE 10E | PETER ATKINS | JULIO DE PAULA ©2014 W. H. FREEMAN AND COMPANY PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN ©2014 W. H. FREEMAN D COMPANY

CHAPTER 6: FIGURE 6B.4 PHYSICAL CHEMISTRY: THERMODYNAMICS, STRUCTURE, AND CHANGE 10E | PETER ATKINS | JULIO DE PAULA ©2014 W. H. FREEMAN AND COMPANY PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN ©2014 W. H. FREEMAN D COMPANY

Some electrochemical terminology: An electrochemical cell: two electrodes (conductors, usually metallic) in contact with an electrolyte (ionic conductor) Electrolyte could be solution, liquid or solid Electrode + electrolyte form electrode compartment Electrode compartments can share same electrolyte or be connected by a salt bridge (e.g. conc. solution of salt in agar jelly) Galvanic cell (battery) produces voltage difference between the two electrodes by spontaneous chemical reactions inside cell. Fuel cells are variations of galvanic cells that allow continuous reactant input. Electrolytic cells: non-spontaneous reactions driven by applying a voltage  work is done on system!

CHAPTER 6: FIGURE 6C.3 PHYSICAL CHEMISTRY: THERMODYNAMICS, STRUCTURE, AND CHANGE 10E | PETER ATKINS | JULIO DE PAULA ©2014 W. H. FREEMAN AND COMPANY PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN ©2014 W. H. FREEMAN D COMPANY

Express redox reactions via two half-reactions Example: Water oxidation 2 H2O  4e- + 4H+ + O2 4e- + 4H+  2H2 Reduced and oxidized species form a redox couple; Example: Dissolution of AgCl - difference of 2 reduction half-reactions AgCl(s) + e-  Ag(s) + Cl- Redox couple: AgCl/Ag,Cl- Ag+(aq) + e-  Ag(s) Redox couple: Ag+/Ag (see Table 6C.1 in book) Electrons move “alphabetically” from anode to cathode in the outer circuit Oxidation takes place at the anode, reduction at the cathode “Reduction on the Right”

CHAPTER 6: TABLE 6C.1 PHYSICAL CHEMISTRY: THERMODYNAMICS, STRUCTURE, AND CHANGE 10E | PETER ATKINS | JULIO DE PAULA ©2014 W. H. FREEMAN AND COMPANY PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN ©2014 W. H. FREEMAN D COMPANY

CHAPTER 6: FIGURE 6C.1 PHYSICAL CHEMISTRY: THERMODYNAMICS, STRUCTURE, AND CHANGE 10E | PETER ATKINS | JULIO DE PAULA ©2014 W. H. FREEMAN AND COMPANY PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN ©2014 W. H. FREEMAN D COMPANY

Example: The Daniell Cell (Figures 6C.1, 6C.2) Half-reactions: Reduction: Cu2+(aq) + 2e-  Cu(s) Redox couple Cu2+/Cu Oxidation: Zn(s)  Zn2+(aq) + 2e- Redox couple Zn2+/Zn Overall reaction: sum of the two half-reactions: Cu2+(aq) + Zn  Cu(s) + Zn2+ Connecting anode and cathode in the outer circuit  el. current flows until equilibrium is established between ions and metal.   Shorthand cell notation (convention) single vertical line |  phase boundary vertical dots :  liquid junction (can give rise to potential difference at the junction, “junction potential”) double vertical line ||  interface with essentially zero junction potential (e.g. salt bridge)

CHAPTER 6: FIGURE 6C.2 PHYSICAL CHEMISTRY: THERMODYNAMICS, STRUCTURE, AND CHANGE 10E | PETER ATKINS | JULIO DE PAULA ©2014 W. H. FREEMAN AND COMPANY PHYSICAL CHEMISTRY: QUANTA, MATTER, AND CHANGE 2E| PETER ATKINS| JULIO DE PAULA | RONALD FRIEDMAN ©2014 W. H. FREEMAN D COMPANY