Redox Reactions

Definition and Basics:

A Redox reaction is a chemical reaction that involves a transfer of electrons between two species.
This reaction comprises two half reactions— oxidation (where electrons are lost) and reduction (where electrons are gained).
The species gaining the electrons is the oxidising agent (or oxidant) and the species losing the electrons is the reducing agent (or reductant).
Redox reactions form the basis of electricity generation in batteries and fuel cells.

Balancing Redox Reactions:

Oxidation numbers help to balance chemical equations in redox reactions.
Oxidation number of an atom increases if it loses electrons and decreases if it gains electrons.
Half-equation method is an efficient process to balance redox equations by balancing oxidation and reduction half-equations separately, and then adding them together.

Identifying Redox Reactions:

Presence of a change in the oxidation states of some atoms in the reactants indicates a redox reaction.
A redox reaction always involves a change in the oxidation number of at least two elements.

Redox Reactions in Metallurgy:

Redox reactions play a central role in the extraction of metals. Ores are often compounds of the metal with oxygen, sulphur or a halogen.
The metal species are reduced to their elemental form by the loss of oxygen, gain of hydrogen or loss of a more electronegative element.
Important metallurgical processes like roasting and smelting are based on redox principles.

Redox Titrations:

In Redox titration, the reaction between the analyte and titrant forms the basis for quantitative chemical analysis.
Commonly used reagents for redox titration include potassium permanganate, potassium dichromate, and iodine – often used as oxidising agents.

Real-World Applications:

Redox reactions are employed in numerous practical applications including energy production, such as in batteries and fuel cells, and various industrial processes like metal extraction.
Corrosion can be understood as a redox process. For example, rusting of iron is a redox reaction with oxygen (from air) and water.