Electrolysis Lecture Notes

Definition of Electrolysis

• Electrolysis: Flow of electrical current through a liquid causing chemical changes.
• Current can flow through:
  • Molten ionic compounds
  • Aqueous solutions
• The liquid must be able to carry current.

Example: Table Salt (NaCl)

• Heating sodium chloride >801°C melts it.
• Free-flowing ions:
  • Positive sodium ions (cations)
  • Negative chloride ions (anions)
  • Ions are free to move within the liquid.

Electrodes in Electrolysis

• Use two electrical conductors (e.g., copper due to high melting point).
• Initially, no reaction with ions until connected to a power supply.
• Connecting electrodes to an electrical cell creates:
  • Positive and negative electrodes.

Electrical Current in Metals

• Electrons in metals form a "sea of electrons".
• Electrons drift towards positive terminal when voltage is applied.
• Current is the movement of charge (electrons).

Process of Electrolysis in Molten NaCl

• Connect electrodes to cell:
  • Electrons flow, causing positive charge on one electrode, negative on the other.
  • Sodium ions (cations) are attracted to negative electrode (cathode).
  • Chloride ions (anions) are attracted to positive electrode (anode).
  • Opposite charges attract.

Chemical Reactions at Electrodes

• Electron exchange at electrodes triggers chemical reactions:
  • Formation of solids, release of gases, or new solutions created.

Special Names for Electrodes

• Anode: Positive electrode, attracts anions.
• Cathode: Negative electrode, attracts cations.

Characteristics of Electrolytes

• Conducting solution or molten liquid is an electrolyte.
• Charge carriers in the liquid are ions.
• Electrolysis can occur in both molten compounds and ionic solutions.
• Conductivity influenced by:
  • Concentration of the solution
  • Potential difference (voltage)

Summary of Key Ideas

• Electrolysis causes chemical changes through electrical current in a conducting liquid.
• Electrolyte has free moving ions.
• Electrodes inserted into electrolyte conduct electrical charge.
• Cations: Positive ions, move to cathode.
• Anions: Negative ions, move to anode.
• Electrons move and carry charge in electrodes and wires.

These notes provide a summary of the key concepts related to electrolysis, emphasizing the conditions required for the process and the nature of the chemical reactions involved.