Introduction
Redox reactions are central to electrochemistry. The word Redox is a combination of Reduction and Oxidation, describing chemical processes that involve the transfer of electrons. These reactions occur in various phenomena such as rusting, respiration, combustion, and electrolysis.

Key Concepts

1. Oxidation

• Classical: Addition of oxygen or removal of hydrogen.

• Modern: Loss of electrons by a substance.

2. Reduction

• Classical: Removal of oxygen or addition of hydrogen.

• Modern: Gain of electrons by a substance.

Mnemonic – OIL RIG

• Oxidation Is Loss (of electrons)

• Reduction Is Gain (of electrons)

Half Reactions
Redox reactions can be split into two half-equations:

• Oxidation half: Zn → Zn²⁺ + 2e⁻

• Reduction half: Cu²⁺ + 2e⁻ → Cu

Combined Reaction:
Zn + Cu²⁺ → Zn²⁺ + Cu

Oxidizing and Reducing Agents

• Oxidizing agent: Accepts electrons (is reduced)

• Reducing agent: Donates electrons (is oxidized)

NECTA-Style Example

Question:
In the reaction:
2Mg + O₂ → 2MgO
Identify the oxidizing and reducing agents.

Answer:

• Mg is oxidized (loses electrons)

• O₂ is reduced (gains electrons)

• Mg is the reducing agent

• O₂ is the oxidizing agent

Real-Life Applications

• Dry cells (e.g., Zinc-carbon batteries)

• Respiration (oxidation of glucose)

• Corrosion and rust prevention

• Extraction of metals (e.g., electrolysis of Al)

Summary

• Redox involves simultaneous oxidation and reduction.

• Oxidation: loss of electrons.

• Reduction: gain of electrons.

• Always identify the agents and electron flow.