Electrochemistry Part 1: Electrolysis

Introduction

• Electrolysis: Decomposition of an ionic compound when molten or in aqueous solution through the passage of electric current.
• Involves breaking apart ionic compounds using electricity.
  • Ionic compounds must be melted or dissolved in water to have free ions, allowing electricity to pass through.

Electrolytic Cell Components

• Electrode: A conductor (often metal or graphite rod) that allows electric current to enter or exit an electrolyte.
• Electrolyte: The molten or aqueous substance that undergoes electrolysis:
  • Molten: Heated until it becomes liquid.
  • Aqueous: Dissolved in water.

Ions and Charges

• Cation: Positively charged ion (loses electrons).
• Anion: Negatively charged ion (gains electrons).
• Cathode: Negative electrode, attracts cations.
• Anode: Positive electrode, attracts anions.

Remembering Electrode Charges

• Cathode: Attracts cations (positive ions), so it is negative.
• Anode: Attracts anions (negative ions), so it is positive.

Process of Electrolysis

• Electric current flows through the circuit and carries the charge:
  • Electrons move from power supply to cathode, making it negative.
  • Anode becomes positive as it loses electrons.
• Cations move to the cathode and gain electrons.
• Anions move to anode and lose electrons.
• Electrons from the anode return to power supply.

Ion Movement and Charge

• In electrodes and wires: Electrons carry the charge.
• In electrolyte: Ions move and carry electrical charge.

Predicting Products of Electrolysis

• Cation will move towards the cathode.
• Anion will move towards the anode.
• Electrolyte can be molten compound or aqueous solution.
  • Binary compound: Composed of two different elements.
• Example: Electrolysis of molten sodium chloride (NaCl):
  • Ions: Na⁺ and Cl⁻.

Electron Movement at Electrodes

• Oxidation (at anode): Loss of electrons by anions.
• Reduction (at cathode): Gain of electrons by cations.
  • Mnemonic: OIL RIG - Oxidation Is Loss, Reduction Is Gain.

Writing Ionic Half Equations

• Show processes ensuring charges are balanced.
• Example: Electrolysis of molten sodium chloride:
  • Anode: 2 Cl⁻ → Cl₂ + 2 e⁻ (Chloride ions lose electrons forming Cl₂ gas).
  • Cathode: Na⁺ + e⁻ → Na (Sodium ions gain electrons).

Conclusion

• Part one concludes with understanding basic concepts of electrolysis and electron movement.
• Encouragement to support and subscribe for more educational content.