Notes on Electrolysis

Definition of Electrolysis

• Electrolysis: The process of electrical current flowing through a liquid, causing chemical changes.
  • Current must flow through a conducting liquid.
  • Conducting liquids can be:
    • Molten ionic compounds
    • Aqueous solutions

Conductivity of Liquids

• Not all liquids can conduct electricity.
• Example: Sodium Chloride (NaCl)
  • Melting point: 801°C (becomes molten)
  • Free-flowing ions in molten NaCl:
    • Cations: Positive sodium ions
    • Anions: Negative chloride ions

Electrodes and Electrical Current

• Electrodes: Two electrical conductors submerged in the liquid (e.g., copper).
• When connected to a power supply:
  • Electrons flow in the wires.
  • One electrode becomes positively charged and the other negatively charged.

Behavior of Electrons in Metals

• Electrons in metals form a sea of electrons that move easily under voltage.
• Current: Movement of charge (in this case, electrons).

Interaction in Molten Sodium Chloride

• Attraction of Ions:
  • Sodium (Na+) attracted to the negative electrode (cathode).
  • Chloride (Cl-) attracted to the positive electrode (anode).
• Chemical Reactions: Electron exchange occurs at the electrodes, leading to:
  • Formation of solids
  • Release of gases
  • Creation of new solutions

Types of Electrodes

• Anode: Positive electrode (attracts anions).
• Cathode: Negative electrode (attracts cations).

Conductivity and Electrolytes

• A liquid that can conduct electricity through free-moving ions is called an electrolyte.
• Electrolysis can occur in both:
  • Ionic solutions
  • Molten compounds

Factors Affecting Electrolysis

• Concentration of the solution: More concentrated solutions result in greater ion flow rate.
• Potential difference (voltage): Increasing voltage enhances ion flow rate.

Summary of Key Ideas

• Electrolysis involves the flow of electrical current in a conducting solution or molten liquid, causing chemical changes.
• Electrolyte: The conducting liquid with free-moving ions.
• Electrodes: Plates or wires inserted into the electrolyte.
• Cations: Positive ions attracted to the cathode.
• Anions: Negative ions attracted to the anode.
• Movement of ions carries electrical charge in the electrolyte, while movement of electrons carries the charge in the electrodes and wires.