Electrolysis Notes

Definition of Electrolysis

• Electrolysis is the flow of electrical current through a liquid that causes chemical changes.
• This process requires a conducting liquid, which can be a molten ionic compound or an aqueous solution.

Conductivity of Liquids

• Not all liquids can conduct electricity.
• The liquid must contain free-moving ions.

Example: Sodium Chloride (NaCl)

• Heating sodium chloride to over 801°C melts it, resulting in free-flowing sodium cations (positive) and chloride anions (negative).
• Cations are positively charged ions; anions are negatively charged ions.

Electrodes and Electrical Supply

• Electrodes are conductors inserted into the liquid (e.g., copper wires).
• When connected to an electrical cell, the electrodes create a potential difference.

Behavior of Electrons

• Electrons in metals move freely, forming a 'sea of electrons'.
• When voltage is applied, electrons drift towards the positive terminal of the battery, resulting in current flow.

Electrolysis Process

• Upon connecting electrodes to an electrical cell:
  • One electrode becomes positively charged (anode) and the other negatively charged (cathode).
• Ionic Movement:
  • Sodium cations are attracted to the cathode (negative electrode).
  • Chloride anions are attracted to the anode (positive electrode).
• When ions meet electrodes, electron exchange occurs, triggering chemical reactions (e.g., solid formation, gas release).

Electrode Definitions

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

Electrolytes

• A liquid that contains free-moving ions and can conduct electricity is called an electrolyte.
• Electrolysis can occur in both ionic solutions and molten compounds.

Factors Affecting Ion Flow

• Concentration: More concentrated solutions have a greater ion flow rate.
• Potential Difference: Increasing voltage across the cell also increases ion flow rate.

Key Takeaways

• Electrolysis causes chemical changes through the flow of electrical current in a conducting solution or molten liquid.
• The liquid is called an electrolyte, and the conductors are called electrodes.
• Movement during electrolysis:
  • Ions in the liquid carry the charge in the electrolyte.
  • Electrons in the electrodes and wires carry the charge in the electrical circuit.