Redox – GCSE Chemistry (Triple) CCEA Revision

Redox Reactions

Redox is an abbreviation of “reduction and oxidation”, the two types of reactions that occur simultaneously in a redox reaction.
Oxidation refers to the loss of electrons from a particle, increasing its oxidation state. The increase is due to the presence of more positively charged protons than negatively charged electrons.
Reduction refers to the gain of electrons by a particle, decreasing its oxidation state. The decrease is due to the availability of more negatively charged electrons than positively charged protons.
An element that loses electrons and is oxidised is known as a reducing agent because it enables another substance to be reduced.
An element that gains electrons and is reduced is known as the oxidising agent because it enables another substance to be oxidised.
Remember: OIL RIG - Oxidation Is Loss, Reduction Is Gain (of electrons).

Redox reactions have numerous applications in daily life, including electrochemical cells (like batteries), respiration processes in cells, combustion processes, electroplating, and the corrosion of metals.
Corrosion is an example of a real-world redox reaction where iron, for example, reacts with oxygen in the air to form hydrated iron(III) oxide, commonly known as rust. Iron is oxidised while oxygen is reduced.
Respiration is an essential redox process that occurs in living organisms where glucose is oxidised to carbon dioxide, releasing energy for other metabolic processes, while oxygen is reduced to water.

Redox reactions are extensively utilised in various industrial processes, like the Haber process for ammonia production where nitrogen is reduced by hydrogen to form ammonia.
In the contact process, sulphur dioxide is oxidised to form sulphur trioxide in the production of sulphuric acid.

To balance redox reactions, one can use the ‘half equation’ method, which separates the oxidation and reduction processes into two half-equations. This helps to understand and balance the overall reaction effectively.
In balancing redox equations, it’s essential to remember that the total increase in the oxidation numbers of the oxidised species must equal the total decrease in the oxidation numbers of the reduced species. This ensures the conservation of charge and mass.

Gaining a strong understanding of redox reactions equips one with the ability to predict and understand various chemical reactions and situations. It forms the basis for several essential concepts, like electrochemistry, corrosion, as well as energy production and transfer in biological systems.