Conductor versus Electrolyte

Introduction to Electrolysis

• Electrolysis: Process of electrically inducing chemical changes in a conducting melt or solution.
• Main Concept: Splitting of ionic compounds into metals and non-metals.
• Conduction: Via freely moving charged particles under a voltage.

Electrical Conductors and Electrolytes

Conductors

• Materials that conduct electricity through free or delocalized electrons.
• Examples: All metals (molten or solid), carbon (graphite).

Electrolytes

• Liquid containing free moving ions capable of conducting electricity.
• Ions: Charged particles such as Na⁺ (sodium ion) or Cl⁻ (chloride ion).

Differences between Conductors and Electrolytes

• Conductor: Current flows through solid metals via free electrons.
  • No chemical change occurs.
  • Returns to original state once the current stops.
• Electrolyte: Current flows in molten or dissolved states through ions.
  • Chemical change occurs at the electrodes.
  • Chemical changes are irreversible.

Circuit for Electrolysis

• Ion Currents: Cations move to the cathode, anions move to the anode.
• Resistance: Decreases with increased concentration of electrolyte ions.
• Typically involves acids, alkalis, or salts.

Key Definitions

• Electrolysis: Decomposition of substances in a molten state or solution by electricity.
• Electrolyte: Compound conducting electricity when molten or in solution.
• Non-electrolyte: Does not conduct electricity in any state.
• Electrodes: Metal strips facilitating conduction in electrolytes.
• Electrolytic Cell: Setup for performing electrolysis; includes vessel, electrodes, battery.

Electrolysis Processes

Example: Lead(II) Bromide

• Reactions:
  • Anode: Oxidation of bromide ions to bromine gas.
  • Cathode: Reduction of lead(II) ions to lead.

Example: Water

• Reactions:
  • Cathode: Reduction of hydrogen ions to hydrogen gas.
  • Anode: Oxidation of hydroxide ions to oxygen gas.

Example: Sodium Chloride Solution

• Reactions:
  • Cathode: Hydrogen ions reduced, generating hydrogen gas.
  • Anode: Chloride ions oxidized, generating chlorine gas.

Example: Copper (II) Sulphate Solution

• Reactions:
  • Cathode: Copper ions reduced, copper deposited.
  • Anode: Hydroxide ions oxidized, generating oxygen gas.

Electrolysis with Copper Electrodes

• Copper ions are consistently reduced and dissolved, maintaining concentration.
• Used for purification of copper.

Applications of Electrolysis

Electroplating

• Process of coating an object with a layer of metal using electrolysis.
• Enhances appearance and prolongs life.
• Requires direct current for smooth coating.

Electro-refining

• Purification of impure metals like copper via electrolysis.
• Involves deposition of pure metal at the cathode.

Aluminium Extraction

• Aluminium extracted from bauxite via electrolysis.
• Cell Reactions:
  • Cathode: Reduction of aluminium ions.
  • Anode: Formation and combustion of oxygen with carbon.
• Economic Concerns: High electricity and material costs.
• Environmental Impact: Pollution from mining and processing.
• Recycling: Saves energy, reduces environmental impact.

Uses of Aluminium

• Used in aircraft, transport, overhead cables, and cookware due to its low weight, strength, and corrosion resistance.

Mathematical Example

• Example relating to moles of metals deposited during electrolysis.

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These notes capture the core concepts and examples provided in the document, offering a structured overview of the subject matter related to electrolysis.