How do redox reactions relate to electrochemical cells?

Redox reactions are the fundamental processes that occur in electrochemical cells, driving the production of electrical energy.

In more detail, redox reactions, short for reduction-oxidation reactions, are chemical reactions where the oxidation states of atoms are changed. This involves the transfer of electrons from one substance to another. In an electrochemical cell, these reactions are separated into two half-reactions: oxidation (loss of electrons) and reduction (gain of electrons). These reactions occur at the two electrodes of the cell, the anode and the cathode.

The anode is where oxidation occurs. Here, a substance loses electrons and becomes positively charged. These electrons are then transferred through the external circuit to the cathode. This movement of electrons is what we observe as electric current. At the cathode, the reduction reaction takes place. A different substance gains the electrons that have been lost by the oxidised substance, becoming negatively charged.

The overall cell reaction is the sum of the oxidation and reduction half-reactions. The ability of the cell to do work, or its electromotive force (EMF), is determined by the difference in potential energy between the anode and cathode. This is also known as the cell potential or cell voltage.

In summary, redox reactions are integral to the functioning of electrochemical cells. They facilitate the transfer of electrons from the anode to the cathode, generating an electric current. Understanding these reactions is key to understanding how electrochemical cells, such as batteries, work.