Lecture notes Unit 3.1.7 - Oxidation, reduction and redox equations

Oxidation, reduction, and redox equations are fundamental concepts in chemistry, particularly in the study of chemical reactions involving electron transfer. Oxidation Definition: Oxidation is the process where an atom, ion, or molecule loses one or more electrons. Oxidation State: The oxidation state (or oxidation number) of the species increases. Example: In the reaction Fe → Fe 2 + + 2 e − Fe→Fe 2+ +2e − , iron (Fe) is oxidized to iron(II) ion (Fe²⁺). Reduction Definition: Reduction is the process where an atom, ion, or molecule gains one or more electrons. Oxidation State: The oxidation state of the species decreases. Example: In the reaction Cl 2 + 2 e − → 2 Cl − Cl 2 ​ +2e − →2Cl − , chlorine (Cl₂) is reduced to chloride ions (Cl⁻). Redox Equations Definition: Redox equations describe reactions where both oxidation and reduction processes occur simultaneously. Electron Transfer: One species is oxidized (loses electrons) while another is reduced (gains electrons). Balancing: Redox equations are balanced by ensuring both mass and charge are conserved. This often involves splitting the reaction into two half-reactions, one for oxidation and one for reduction, then combining them. Example of a Redox Equation Consider the reaction between zinc and copper(II) sulfate: Zn + CuSO 4 → ZnSO 4 + Cu Zn+CuSO 4 ​ →ZnSO 4 ​ +Cu This can be split into two half-reactions: Oxidation half-reaction: Zn → Zn 2 + + 2 e − Zn→Zn 2+ +2e − (zinc is oxidized) Reduction half-reaction: Cu 2 + + 2 e − → Cu Cu 2+ +2e − →Cu (copper is reduced) Combining these half-reactions gives the balanced redox equation: Zn + Cu 2 + → Zn 2 + + Cu Zn+Cu 2+ →Zn 2+ +Cu In summary, oxidation involves the loss of electrons, reduction involves the gain of electrons, and redox equations describe the overall electron transfer between species in a chemical reaction.