Electrode and Cell Potentials

Introduction

• In a circuit, the flow of charge is a result of an electrical potential difference between two points in the circuit.
• Electrical potential: the ability of the electric field to do work on the charge. 
• Cell potential: electrical potential difference in a galvanic cell

Standard Potentials (E°)

• The driving force of an electrochemical reaction is measured by the standard cell potential.  
• Depends on the nature of the redox reaction and on the concentration of species involved.
• Standard potentials (E°) are measured with 
    * All aqueous concentrations at 1M
    * The pressure of all gases at 1 atm
    * Temperature held constant (usually at 25 °C)
    * Units of E° is V or mV

E° Cathode and Anode

• E°cell = E°cathode - E°anode
• The E° for a half-reaction cannot be measured; only E°cell of the entire redox reaction can be measured.
• When finding E°* for a cell it is useful to remember that you MUST change the sign of E°*(from table) in ONE of the two half cells. 
• Do not multiply those E° values by coefficients!