# D39.1 Oxidation-reduction Reactions and Electrochemistry

Electrochemistry deals with chemical reactions that involve transfer of electron density—reactions either producing electricity or are caused by passage of electrical current through matter. These reactions are called oxidation-reduction (abbreviated as redox) reactions.

Here’s a brief list of units and definitions used when discussing redox reactions and their applications.

• The SI unit of electric charge is the coulomb, C.
• The elementary unit of charge is the charge of a single electron, which is equal to 1.602 × 10−19 C.
• Movement of electrons (or ions) carry electric charges from one place to another, and the quantity of such charge transferred per unit time is the electric current.
• Current has the SI unit ampere, A, which is the transfer of one coulomb per second (1 A = 1 C/s).
• Typically, electric current flows in a closed path, called an electric circuit.
• It is necessary to maintain a closed circuit for current to flow. If the circuit is open, current will not flow.
• Electrical potential, SI unit volt, V, is the ability of an electric field to do work on a charge.
• A flow of charge is caused by an electrical potential difference between two points in the circuit.
• When 1 coulomb of charge moves through a potential difference of 1 volt, it gains or loses 1 joule of energy (1 J = 1 C × 1 V).
• Electric power is the quantity of energy transferred per unit time and is measured in watts, W (1 W = 1 J/ s).

Exercise: Electric Energy and Flow of Charge 