17
Electrochemistry I:
Batteries and Free Energy
Many of the simplest chemical reactions involve only an interchange of atoms
or ions between reactants, or perhaps only the dissociation of one reactant into
two parts. In such reactions, there is no change in the electrical charge of any of
the atoms involved. This chapter deals with another type of reaction, in which
one or more electrons are transferred between atoms, with the result that some
of the atoms involved do have their electrical charges changed. These reactions
are known as electron-transfer reactions. You can appreciate their importance
when you realize that every battery used in electronic devices and machines,
every impulse involved in nerve transmission, every metabolic reaction that
produces energy in biological systems, photosynthesis, and combustion processes (to mention but a few examples) requires electron-transfer reactions.
ELECTRON-TRANSFER POTENTIAL
Oxidation and Reduction
In the transfer of electrons between atoms, an electron donor is called a reducing agent; an electron acceptor is called an oxidizing agent. Whenever a reducing agent donates electrons, we say that it has been oxidized; we say that an
oxidizing agent, on accepting electrons, has been reduced. Oxidation and reduction always occur simultaneously; if one atom or ion donates an electron,
another atom or ion must accept it.
Electrochemistry I:
Batteries and Free Energy
Many of the simplest chemical reactions involve only an interchange of atoms
or ions between reactants, or perhaps only the dissociation of one reactant into
two parts. In such reactions, there is no change in the electrical charge of any of
the atoms involved. This chapter deals with another type of reaction, in which
one or more electrons are transferred between atoms, with the result that some
of the atoms involved do have their electrical charges changed. These reactions
are known as electron-transfer reactions. You can appreciate their importance
when you realize that every battery used in electronic devices and machines,
every impulse involved in nerve transmission, every metabolic reaction that
produces energy in biological systems, photosynthesis, and combustion processes (to mention but a few examples) requires electron-transfer reactions.
ELECTRON-TRANSFER POTENTIAL
Oxidation and Reduction
In the transfer of electrons between atoms, an electron donor is called a reducing agent; an electron acceptor is called an oxidizing agent. Whenever a reducing agent donates electrons, we say that it has been oxidized; we say that an
oxidizing agent, on accepting electrons, has been reduced. Oxidation and reduction always occur simultaneously; if one atom or ion donates an electron,
another atom or ion must accept it.