What is a redox couple?

In chemistry and electrochemistry, a redox couple, short for "reduction-oxidation couple," refers to a pair of chemical species that are involved in a redox reaction. A redox reaction is a type of chemical reaction that involves the transfer of electrons between two chemical species: one species undergoes oxidation by losing electrons, and the other undergoes reduction by gaining those electrons.

In a redox couple, one species acts as the oxidizing agent (accepts electrons) and is referred to as the "oxidizing agent" or the "oxidant." The other species acts as the reducing agent (donates electrons) and is referred to as the "reducing agent" or the "reductant."

The redox couple is represented using the following notation:

Oxidized species (oxidant) / Reduced species (reductant)

For example, consider the redox couple involving iron (Fe) and copper (Cu):

Fe^2+ / Cu

In this redox couple, the iron ion (Fe^2+) is being oxidized to form Fe^3+ (losing one electron), while the copper ion (Cu) is being reduced to form Cu^2+ (gaining one electron).

Redox couples are essential in understanding various chemical reactions, especially in electrochemistry and the operation of electrochemical cells, such as batteries and fuel cells. The transfer of electrons between redox couples drives these electrochemical processes and allows for the conversion of chemical energy into electrical energy and vice versa.