What is the Difference Between Oxidation and Reduction?

The correct answer is: A. Oxidation is a reaction that removes an electron from a substance; reduction is a reaction that adds electrons to a substance.

Complete Explanation

Oxidation is the loss of electrons, while reduction is the gain of electrons; a duality that forms the core of redox reactions. Remember the mnemonic OIL RIG (Oxidation Is Loss, Reduction Is Gain)! But these processes aren’t just about electrons; they also involve changes in oxidation states and are inseparable in chemical reactions. 

In simple terms:

• Oxidation = losing electrons
• Reduction = gaining electrons

An easy way to remember this is the phrase OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons).

So, when a substance loses electrons, it is being oxidized.

When a substance gains electrons, it is being reduced.

Electron Transfer is the Heart of Oxidation and Reduction

At the atomic level, oxidation and reduction are all about electrons:

• Oxidation: When a substance loses electrons
  (e.g., iron rusting: Fe → Fe³⁺ + 3e⁻).
• Reduction: When a substance gains electrons
  (e.g., oxygen in rusting: O₂ + 4e⁻ → 2O²⁻).

These processes always occur together, like a seesaw. If one molecule loses electrons (oxidation), another must gain them (reduction).

Oxidation States

Oxidation states (or oxidation numbers) help track electron movement:

• Oxidation increases the oxidation state (e.g., Fe from 0 to +3).
• Reduction decreases the oxidation state (e.g., O from 0 to -2).

For example, in the reaction 2Mg + O₂ → 2MgO:

• Magnesium’s oxidation state rises from 0 to +2 (oxidized).
• Oxygen’s oxidation state drops from 0 to -2 (reduced).

Real-World Examples

• Rusting of Iron: Iron loses electrons (oxidation), while oxygen gains them (reduction).
• Combustion: Burning methane (CH₄ + 2O₂ → CO₂ + 2H₂O) involves carbon losing electrons (oxidation) and oxygen gaining them (reduction).
• Batteries: In a lithium-ion battery, lithium atoms lose electrons (oxidation) during discharge, while cobalt oxide gains them (reduction).

Oxidizing vs. Reducing Agents

• Oxidizing agents accept electrons and get reduced (e.g., O₂, KMnO₄).
• Reducing agents donate electrons and get oxidized (e.g., Na, H₂).

In the reaction Zn + Cu²⁺ → Zn²⁺ + Cu:

• Zinc (reducing agent) loses electrons.
• Copper ions (oxidizing agent) gain electrons.

Common Doubts in Chemistry