Glossary
Assigning Oxidation Numbers
The systematic procedure of determining the oxidation state for each atom within a compound or ion by applying a set of established rules.
Example:
Before balancing a complex redox equation, the first crucial step is assigning oxidation numbers to all elements to identify what is being oxidized and reduced.
Balancing Redox Equations
The method used to ensure that both the number of atoms of each element and the total charge are equal on both sides of a redox reaction, often involving half-reactions and the addition of H⁺/OH⁻ and H₂O.
Example:
Mastering balancing redox equations is essential for predicting the stoichiometry of electrochemical reactions, such as those occurring in fuel cells.
Half-reaction
A component of a redox reaction that separately shows either the oxidation or the reduction process, including the electrons transferred.
Example:
The conversion of Fe³⁺ to Fe²⁺ in a biological system can be written as a half-reaction: Fe³⁺(aq) + e⁻ → Fe²⁺(aq).
Oxidation
The process in a redox reaction where a chemical species loses electrons, resulting in an increase in its oxidation state.
Example:
When a silver spoon tarnishes, the silver metal undergoes oxidation, forming silver sulfide and changing its oxidation state from 0 to +1.
Oxidation State
A number assigned to an atom in a molecule or ion that indicates its hypothetical charge if all bonds were purely ionic, reflecting the number of electrons gained, lost, or shared.
Example:
In the compound KMnO₄, manganese has an oxidation state of +7, indicating a high degree of electron deficiency.
Oxidizing Agent
The chemical species that causes another substance to be oxidized by accepting electrons from it, and is itself reduced in the process.
Example:
Hydrogen peroxide (H₂O₂) often acts as an oxidizing agent in bleaching processes, accepting electrons and being reduced to water.
Redox Reactions
Chemical reactions that involve the transfer of electrons between reactants, leading to changes in their oxidation states.
Example:
The process of photosynthesis in plants is a complex series of redox reactions where water is oxidized and carbon dioxide is reduced.
Reducing Agent
The chemical species that causes another substance to be reduced by donating electrons to it, and is itself oxidized in the process.
Example:
In metallurgy, carbon monoxide (CO) is a common reducing agent used to extract metals from their ores, as it donates electrons and is oxidized to carbon dioxide.
Reduction
The process in a redox reaction where a chemical species gains electrons, resulting in a decrease in its oxidation state.
Example:
In a car battery, lead(IV) oxide undergoes reduction to lead(II) sulfate as it gains electrons during discharge.