Lecture 21 (3/11/2013)
The branch of chemistry that examines the transformations
between chemical energy and electrical work.
o Reduction/Oxidation (Redox) Reactions:
Reactions in which substance gain electrons (reduction) or lose
• Electrochemical Cells:
o An apparatus for separating a cell reaction’s reduction and oxidation half
• Surfaces for exchange of electrons.
• Electrode at which an oxidation occurs.
• Electrode at which a reduction occurs.
A bridge connects the two solutions of the cell.
• Voltaic Cell:
o An electrochemical cell in which chemical energy is transformed into
electrical energy by a spontaneous redox reaction.
• Cell Potentials:
o Standard Reduction Potential (E°):
Potential of a reduction halfreaction in which all
reactants/products are in standard states at 25°C (gases = 1 atm,
concentrations = 1 M).
o Standard Cell Potential (E °)cell
Measure of how forcefully an electrochemical cell can pump
electrons through an external circuit (reactants/products in standard
o Electromotive Force (emf):
The force pushing electrons through an electrical circuit (also
• Calculating Cell Potentials: