Electrolysis

Definition

• Electrolysis is the flow of electrical current through a liquid that causes chemical changes.
• Not all liquids can conduct electricity; it must be a molten ionic compound or an aqueous solution that can carry current.

Example: Sodium Chloride

• Table Salt (Sodium Chloride):
  • Melts at over 801°C to become a liquid containing free-flowing ions.
  • Positive sodium ions (cations) and negative chloride ions (anions) are free to move within the molten liquid.

Conductivity and Electrodes

• Electrodes: Conductors inserted into the molten liquid.
  • Example: Copper wires which connect to an electrical cell or power supply.
  • One electrode becomes positively charged (anode) and the other negatively charged (cathode).
• Electrical Current in Metals:
  • In metals, electrons form a 'sea' that can move easily when a potential difference (voltage) is applied.
  • Current is the movement of electrons towards the positive terminal of a battery.

Chemical Reactions in Electrolysis

• Positive ions (cations) are attracted to the negative electrode (cathode).
• Negative ions (anions) are attracted to the positive electrode (anode).
• Electron exchange at the electrodes triggers chemical reactions:
  • Solids can form, gases can be released, and new solutions can emerge.
• Electrolyte: A liquid that conducts electrical current through moving ions.
  • If a liquid has free-moving ions and conducts electricity, it is called an electrolyte.

Factors Affecting Electrolysis

• Electrolysis can occur in both ionic solutions and molten compounds.
• The ion flow rate increases with:
  • Higher concentration of the solution.
  • Increased potential difference (voltage) across the cell.

Summary

• Electrolysis involves electrical current flow in a conducting solution or molten liquid causing chemical changes.
• Key Components:
  • Electrolyte: Conducting liquid with free-moving ions.
  • Electrodes: Conducting plates, bars, or wires inserted into an electrolyte.
  • Cations: Positive ions attracted to the cathode.
  • Anions: Negative ions attracted to the anode.
• Movement of Charge:
  • In electrolyte: Ions move and carry electrical charge.
  • In electrodes/wires: Electrons move and carry electrical charge.