Interactive Chemistry Worksheets for Students
Reduction oxidation reactions are called redox reactions. They involve the transfer of electrons from one species to another and are represented by two half equations, the oxidation half equation and the reduction half equation.
Oxidation half equation: Eg. Mg Mg2+ + 2e- OIL: Oxidation Is Loss of electrons by a chemical species. The Mg species loses electrons and is oxidised.
Reduction half equation: Eg. Cu2+ + 2e- Cu RIG: Reduction Is Gain of electrons by a species. The Cu2+ ion gains electrons and is reduced.
Notice the electrons, symbol e-, are on different sides of the two equations in equal numbers.
Oxidation reduction reactions always occur together. One chemical species loses electrons and the other species gains electrons.
The resulting net reaction is called a redox reaction. Eg. Mg + Cu2+ Mg2+ + Cu
A galvanic cell is a device which separates these two half reactions allowing the electrons to flow through an external wire. We call this device a battery.