Standard Cell Notation (line notation) Conventions: Anode on Left Single line : represent phase boundaries Two line : represent liquid junction Cu2+ V NO3- Zn2+ Cu Zn e- Anode / anode solution // cathode solution / Cathode Example: Zn / Zn2+ (1.0 M) // Cu2+ (1.0M) / Cu

Line Notation solid½Aqueous½½Aqueous½solid Anode on the left½½Cathode on the right Single line different phases. Double line porous disk or salt bridge. If all the substances on one side are aqueous, a platinum electrode is indicated.

For the last reaction Cu(s)½Cu+2(aq)½½Fe+2(aq),Fe+3(aq)½Pt(s)

Oxidation Reduction

Copyright McGraw-Hill 2009

Practice: In a galvanic cell, the electrode that acts as a source of electrons to the solution is called the __________; the chemical change that occurs at this electrode is called________.   a.  cathode, oxidation   b.  anode, reduction   c.  anode, oxidation   d.  cathode, reduction

Practice Under standard conditions, which of the following is the net reaction that occurs in the cell? Cd|Cd2+ || Cu2+|Cu   a.  Cu2+ + Cd → Cu + Cd2+   b.  Cu + Cd → Cu2+ + Cd2+   c.  Cu2+ + Cd2+ → Cu + Cd   d.  Cu + Cd 2+ → Cd + Cu2+ 

Galvanic Cell The reaction always runs spontaneously in the direction that produced a positive cell potential. Four things for a complete description. Cell Potential Direction of flow Designation of anode and cathode Nature of all the components- electrodes and ions

Oxidation Numbers on the Periodic Table

Cell Potential Cell Potential / Electromotive Force (EMF): The “pull” or driving force on electrons Measured voltage (potential difference) The total cell potential is the sum of the potential at each electrode.

Ecell = +1.10 V

Cell Potential, E0cell E0cell cell potential under standard conditions elements in standard states (298 K) solutions: 1 M gases: 1 atm

Practice Completely describe the galvanic cell based on the following half-reactions under standard conditions. MnO4- + 8 H+ +5e- ® Mn+2 + 4H2O Eº=1.51 V Fe+3 +3e- ® Fe(s) Eº=0.036V