Electrochemistry Summary Information
using chemical reactions to do work (i.e. provide electricity) (known as
using electricity to force nonspontaneous reactions (known as
(redox) reactions involve the transfer of electrons from one chemical to
In this example magnesium loses two electrons
and is considered oxidized
Each chlorine gains an electron
and is considered reduced
Things to remember:
Redox reactions always occur in pairs
The charge on any element is zero.
The species being reduced is the oxidizing agent: The species being oxidized is the reducing agent.
Remember the saying:
Determine which element is oxidized and which is reduced in the following reactions:
Silver is reduced (1
0), copper is oxidized (0
); Fluorine is reduced (0
), chlorine is
A more “active” metal will reduce a less active metal (since the more active metal has a greater tendency
to lose electrons.
Also, in general, most metals will reduce most nonmetals.
metals from more active to less active as in the following:
Li, K, Ba, Ca, Na, Mg, Al, Zn, Fe, Cd, Ni, Sn, Pb, Cu, Hg, Ag, Au
In other words, lithium is the most active metal in this list and can therefore reduce the ion of any of the
metals that come after it in the series. (ex. 3Li
By separating the oxidation part of a reaction from the reduction part then connecting them by a wire,
useful work can be done.
As electrons flow from the oxidation side to the reduction side they can pass
through a light bulb, motor, etc., providing power to make them run.
This type of setup is known as a
The difference in potential energy between the two sides (relative to hydrogen) is known as the potential
difference and is measured in
For instance, the reaction between a silver ion and aluminum
metal is 2.46V.
These values are determined from a list of
standard reduction potentials
that gives the
relative tendency for an element or ion to be reduced.
Examine the following diagram of a typical voltaic cell: