Chemistry Lesson Note On Oxidation and Reduction

Topic: Oxidation and Reduction

Class: SS1

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Specific Objectives:

By the end of the lesson, students should be able to:

1. Define oxidation and reduction in terms of oxygen gain/loss, hydrogen gain/loss, and electron transfer.
2. Identify oxidation and reduction reactions using examples.
3. Explain redox (reduction-oxidation) reactions.
4. Identify oxidizing and reducing agents.
5. Write half equations for redox reactions.

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Instructional Materials:

• Oxidation-reduction reaction charts
• Simple redox reaction experiments (e.g., iron rusting, copper and silver nitrate)
• Ball-and-stick molecular models
• Videos/animations showing electron transfer
• pH indicators and hydrogen peroxide

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Lesson Content:

Step 1: Introduction to Oxidation and Reduction

Chemical reactions where substances gain or lose electrons, oxygen, or hydrogen are called redox reactions. These include oxidation and reduction processes.

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Step 2: Definitions of Oxidation and Reduction

In Terms of Oxygen and Hydrogen:

• Oxidation: Gain of oxygen or loss of hydrogen.
• Reduction: Loss of oxygen or gain of hydrogen.

Examples:

• Oxidation:
  2Mg + O₂ → 2MgO (Mg gains oxygen)
• Reduction:
  CuO + H₂ → Cu + H₂O (CuO loses oxygen)

In Terms of Electron Transfer:

• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.

Mnemonic: OIL RIG

• OIL – Oxidation Is Loss (of electrons)
• RIG – Reduction Is Gain (of electrons)

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Step 3: Redox Reactions

A redox reaction involves both oxidation and reduction occurring simultaneously.

Example:
Zn + Cu²⁺ → Zn²⁺ + Cu

• Zn is oxidized (loses electrons)
• Cu²⁺ is reduced (gains electrons)

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Step 4: Oxidizing and Reducing Agents

Term	Meaning	Example
Oxidizing Agent	Causes oxidation (accepts electrons)	Cu²⁺ in the above reaction
Reducing Agent	Causes reduction (donates electrons)	Zn in the above reaction

More Examples:

• KMnO₄, Cl₂ = oxidizing agents
• H₂, CO = reducing agents

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Step 5: Writing Half Equations for Redox Reactions

Example 1:
Reaction: Zn + Cu²⁺ → Zn²⁺ + Cu

Half Equations:

• Oxidation: Zn → Zn²⁺ + 2e⁻
• Reduction: Cu²⁺ + 2e⁻ → Cu

Example 2:
Fe²⁺ + Cl₂ → Fe³⁺ + 2Cl⁻

• Fe²⁺ → Fe³⁺ + e⁻ (oxidation)
• Cl₂ + 2e⁻ → 2Cl⁻ (reduction)

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Evaluation:

1. Define oxidation and reduction in three different ways.
2. Identify the oxidizing and reducing agents in:
   a. H₂ + Cl₂ → 2HCl
   b. Fe + CuSO₄ → FeSO₄ + Cu
3. Write the half equations for the reaction:
   Zn + Cu²⁺ → Zn²⁺ + Cu
4. Explain the concept of redox reactions.
5. State two industrial or everyday applications of redox reactions.

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Homework:

1. Balance and identify the oxidizing and reducing agents in:
   a. Cl₂ + 2NaI → 2NaCl + I₂
   b. 2Fe²⁺ + H₂O₂ + 2H⁺ → 2Fe³⁺ + 2H₂O
2. Explain why rusting of iron is a redox reaction.
3. List five common oxidizing agents and five reducing agents.
4. Draw a labeled diagram showing how electrons are lost or gained during redox.

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Conclusion:

Oxidation and reduction are vital chemical processes in everyday life and industries. Understanding how substances gain or lose oxygen, hydrogen, or electrons helps in identifying redox reactions and their importance in science and technology.