Galvanic/Voltaic Cells

Introduction

• Definition: Devices that use a chemical reaction to create electricity.
• Reaction Type: Oxidation-reduction reaction (redox reaction).
• Common Example: Batteries, which power devices like cell phones and flashlights.

Components of a Voltaic Cell

• Containers: Two beakers or containers.
• Solutions:
  • Zinc sulfate solution in one container.
  • Copper sulfate solution in the other.
• Electrodes:
  • Zinc metal placed in zinc sulfate solution.
  • Copper metal placed in copper sulfate solution.
• Wire Connection: Connects the zinc and copper metals allowing electrons to flow.
• Salt Bridge: Connects the solutions, maintains charge balance but initially left out for simplicity.

Electron Flow and Electricity Generation

• Electrons Movement: From zinc to copper through the wire.
  • Moving electrons create electricity.
  • Can power devices like a light bulb.
• Role of the Salt Bridge: Balances charge by allowing ions to move between solutions.

Detailed Reaction Process

• Zinc Side:
  • Zinc atoms lose electrons (oxidation), become Zn²⁺ ions, and dissolve.
• Copper Side:
  • Cu²⁺ ions gain electrons (reduction), become neutral copper atoms, and deposit on the copper metal.
• Tug of War: Cu²⁺ has a stronger pull than zinc for electrons.

Oxidation-Reduction Details

• Oxidation: Loss of electrons occurs at the zinc electrode (Anode).
• Reduction: Gain of electrons occurs at the copper electrode (Cathode).
• Half Reactions:
  • Oxidation Reaction: [ \text{Zn (s) } \rightarrow \text{ Zn}^{2+} \text{ (aq) } + 2e^- ]
  • Reduction Reaction: [ \text{Cu}^{2+} \text{ (aq) } + 2e^- \rightarrow \text{ Cu (s) } ]

Cell Notation

• Representation:
  • Oxidation half-cell: Zn (s) | Zn²⁺ (aq)
  • Salt bridge: ||
  • Reduction half-cell: Cu²⁺ (aq) | Cu (s)

Function of the Salt Bridge

• Charge Balance:
  • Sodium ions (Na⁺) move to the copper solution.
  • Chloride ions (Cl⁻) move to the zinc solution.
  • Maintains charge neutrality, allowing the continued flow of electrons.

Summary

• Process: Galvanic or voltaic cells convert chemical energy into electrical energy via redox reactions.
• Key Parts: Zinc as anode (oxidation), copper as cathode (reduction), connected by a wire and a salt bridge.
• Overall Reaction: Electrodes change size as the zinc dissolves and copper deposits.
• Understanding: Knowing oxidation and reduction sites and reactions help comprehend how these cells generate electricity.