Electrochemistry Lecture Notes

Introduction

• Electrochemistry explores the relationship between chemical reactions and electricity.
• Previous knowledge includes:
  • Electricity: Flow of charges resulting in electric current.
  • Chemical Reactions: Conversion of reactants to products.
• Focus on how chemical reactions can induce electricity and vice versa.

Main Topics

1. Electrochemical Cells

   • Function as electricity generators through chemical reactions.
   • Examples include dry cells, rechargeable batteries, and car batteries.
   • Used in devices like toy cars, electric torches, mobile phones, calculators, and computers.

2. Electrolysis

   • Process to decompose compounds using electric current.
   • Non-spontaneous under normal conditions but possible with electricity.

3. Corrosion of Metals

   • Chemical reaction where metals degrade, e.g., rusting of iron.
   • Common lab examples include oxidation of magnesium strips.

Electrochemical Cells

• Batteries are practical examples of electrochemical cells.
• Energy Conversion: Chemical energy is converted to electrical energy.
• Electrodes: Comprise positive and negative terminals.
• Examples: Different sized batteries (AA, AAA, 9V etc.) and vehicle batteries.

Activity: Reaction of Zinc with Sulfuric Acid

Materials Needed

• Beaker
• Dilute sulfuric acid (H₂SO₄)
• Zinc strip

Procedure

1. Add dilute sulfuric acid into a beaker.
2. Insert a zinc strip partially into the acid.
3. Observe the dissolution of zinc and release of gas bubbles.

Observations

• Zinc Dissolves: Zinc moves into solution as zinc ions (Zn²⁺).
• Gas Evolution: Hydrogen gas (H₂) is released.

Chemical Reactions

• Dissociation of Sulfuric Acid
  • H₂SO₄ → 2H⁺ + SO₄²⁻
• Zinc Reaction
  • Zn(s) → Zn²⁺(aq) + 2e⁻ (Oxidation)
• Hydrogen Ion Reaction
  • 2H⁺(aq) + 2e⁻ → H₂(g) (Reduction)
• Overall Balanced Reaction
  • Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

Understanding Electrochemical Cells

• Half Reactions: Oxidation and reduction processes.
• Energy Flow: From chemical to electrical energy.
• Concept: Use two electrodes and an external conductor to generate electricity.

Conclusion

• Understanding of electrochemical cells starts with basic reactions.
• Future lessons will focus on constructing a full cell to induce electron flow through an external circuit.

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