Definition - What does Electrochemical Reaction mean?
An electrochemical reaction is a process in which electrons flow between a solid electrode and substance, such as an electrolyte. This flow triggers an electric current through the electrodes, causing the reaction to liberate or absorb heat.
Under different conditions, other types of reactions create an electric current flow. For example, two electrodes in contact with each other result in a reduction and oxidation (redox) reaction, causing a change in the oxidation numbers of all atoms that are part of the reaction.
Corrosionpedia explains Electrochemical Reaction
In electrochemical reactions, an oxidation is essentially the loss of electrons found on the surfaces of an atom, ion or molecule. The opposite of oxidation is reduction, which is the gaining of lost electrons. In these reactions, the oxidation numbers change accordingly. This can be illustrated by a balanced half reaction. This reaction is non-spontaneous, where electricity is used to allow the reaction to occur, versus a spontaneous reaction, which generates electricity .
Here is a sample experiment involving NaCl2, a molten salt sodium chloride. When salt is molten, it dissociates to its ions - Na+ (cation) and Cl- (anion).
The accompanying reaction is: Na+ + e- --> Na
The anode is the other electrode that supplies the electrons. Here, oxidation is evident, and the half equation is as follows: 2Cl --> Cl2 + 2e-
When aqueous solutions are used in the experiment, additional reactions are evident. The simplest redox reaction for this is the following:
- In the cathode: 2H2O + 2e- --> H2 + 2OH- (Water is reduced.)
- In the anode: 2H2O --> 4H+ + O2 + 4e- (Water is oxidized.)
In conclusion, there is a rule that determine the reactions that take place at each electrode. When the cation in use is an active metal, water is reduced in the cathode. In the anode, water is oxidized when the anion is a polyatomic ion. The anions include suphates and nitrates.