UNIT: 9.8 In-Depth Notes on Galvanic Cells

Overview of Galvanic Cells

  • A part of electrochemistry: study of chemical and electrical energy interactions.
  • Galvanic cells (or voltaic cells): convert chemical reactions into electrical power.

Key Concepts in Redox Reactions

  • Redox Reactions: Involve reduction (gain of electrons) and oxidation (loss of electrons).
    • Mnemonics: "Leo the Lion says GER"
    • Loss of electrons = Oxidation (charge increases)
    • Gain of electrons = Reduction (charge decreases)
  • Redox reactions can be split into two half reactions:
    • Oxidation Half Reaction: Substance loses electrons (e.g.
      zinc turning from solid to ion form).
    • Reduction Half Reaction: Substance gains electrons (e.g. copper ions becoming solid).

Galvanic Cell Construction

  • Basic Setup: Two beakers connected by a wire, with electrodes made of different metals.
    • Zinc Electrode (Anode): Solid zinc is oxidized to zinc ions (Zn²⁺).
    • Copper Electrode (Cathode): Copper ions (Cu²⁺) are reduced to solid copper.
  • Electron Flow: Electrons flow from the oxidation side (anode) to the reduction side (cathode) through the wire, creating electrical current.
    • Completion of Circuit: Requires both electrodes and a salt bridge to maintain charge balance.

Salt Bridge Functionality

  • Purpose of Salt Bridge:
    • Completes the circuit and maintains charge balance by allowing ions to flow in response to charge buildup.
    • Spectator ions (e.g., Na⁺ and NO₃⁻) migrate to counteract negative and positive charge buildups, respectively.

Changes During Reactions

  • Mass Changes: As the reaction occurs:
    • Zinc Electrode: Loses mass as zinc atoms are converted to ions.
    • Copper Electrode: Gains mass as copper ions are deposited onto the electrode as solid metal.
  • Identifying Anodes and Cathodes:
    • Anode: Site of oxidation, mass decreases (where electrons outflow from).
    • Cathode: Site of reduction, mass increases (where electrons inflow to).
    • Convention: Anode (oxidation) always starts with a vowel, just like oxidation (both start with 'a' and 'o').

Voltage Measurement and Future Lessons

  • Use a voltmeter in the circuit to measure how much electricity flows through the wire without impeding electron flow.
  • Next lesson will focus on calculating the voltage produced by a galvanic cell (battery).

Considerations for Non-Solid Electrodes

  • If half reactions don't involve solid electrodes, we cannot run a galvanic cell.
  • Must always include two solid metal electrodes for the cell to operate effectively.

Final Remarks

  • Understand the parts and processes in a galvanic cell to facilitate successful electrical energy generation.
  • Future lessons will put this knowledge to practical use by examining voltage output and calculations.