Electrochemical Reactions and Cells

Overview

Redux Reactions: Involve the transfer of electrons between substances.
- Oxidation: Loss of electrons.
- Reduction: Gain of electrons.
Metal Reactions: More reactive metals (like zinc) lose electrons to less reactive ones (like copper).

Electrochemical Cells: Use Redux reactions to generate or require electrical current.
- Voltaic (Galvanic) Cell: Spontaneous Redux reaction generates current.
- Electrolytic Cell: External current drives a non-spontaneous Redux reaction.

Structure: Composed of two half-cells with separate electrolytes.
- Anode: Site of oxidation (negative electrode).
- Cathode: Site of reduction (positive electrode).
- Salt Bridge: Completes the circuit, balances charge without mixing solutions.
Example: Zinc-copper cell.
- Zinc Anode: Oxidizes zinc to zinc ions, loses mass.
- Copper Cathode: Reduces copper ions to copper metal, gains mass.
Current Flow:
- Negative Charge: Electrons flow clockwise.
- Positive Charge: Conventional current flows counterclockwise.

Structure: External power source creates potential, electrodes submerged in the same electrolyte.
- Anode: Positive electrode, site of oxidation.
- Cathode: Negative electrode, site of reduction.
Electrolysis: Breakdown of substances, e.g., water or molten salts.
- Example: Electrolysis of lead bromide.
  - Lead: Reduced at cathode, collected as metal.
  - Bromine: Oxidized at anode, collected as vapor.

Cell Potential: Drives reaction, decreases over time as reactants are consumed.
Primary Cells: Irreversible reactions, non-rechargeable (e.g., alkaline batteries).
Secondary Cells: Reversible reactions, rechargeable (e.g., smartphone batteries).

Industrial and Energy Applications: Vital for processes and energy storage, crucial for tackling climate change.
Educational Value: Essential knowledge for IB chemistry students aiming to impact the world.