Introduction and Summary
Galvanic Cells allow us to harness the electron flow in a redox
reaction to
perform useful work. Such cells find common use as batteries, pH
meters, and as fuel cells. The setup of the cell, as seen in ,
requires that the oxidation and reduction half-reactions are connected by a wire
and by a salt bridge or porous disk. Electrons will flow through that wire
creating an electrical current. The salt bridge or porous disk allows the passage
of ions in solution to maintain charge neutrality in each half-cell. Instead of
drawing the setup of every cell like , chemists have devised a shorthand
line notation discussed in Line Notation.
The direction of the current in a cell is determined by the standard
reduction potential
of each half-cell. For a reaction to be spontaneous, the overall cell
potential must be
positive (the rules for adding cell potentials are covered under Adding
potentials).
Therefore, the half-reaction with the greater reduction potential will be a
reduction and the
other half-reaction will be an oxidation. The electrode in the
oxidation half-reaction is
called the anode. The electrode in the reduction half-reaction is
called the
cathode.
