Electrochemistry - Electrolysis

Introduction

• Electrolysis: Decomposition of an ionic compound when molten or in aqueous solution by an electric current.
• Key condition: Ionic compound must be melted or in water to have free ions for electricity passage.

Electrolytic Cell Components

• Electrode: A conductor (metal or graphite rod) allowing electric current passage in/out of an electrolyte.
• Electrolyte: Molten or aqueous substance undergoing electrolysis.
  • Molten: Heated until liquid.
  • Aqueous: Dissolved in water.

Ions and Charge

• Cation: Positively charged ion (loses electrons).
• Anion: Negatively charged ion (gains electrons).

Electrodes

• Cathode: Negative electrode.
  • Attracts positively charged cations.
  • Tip: Both "cathode" and "cation" start with "cat".
• Anode: Positive electrode.
  • Attracts negatively charged anions.
  • Tip: Both "anode" and "anion" start with "an".

Electric Current and Electron Flow

• Electrons carry electric charge through the external circuit.
• Cathode:
  • Gains electrons (negative charge).
  • Positive cations move here to gain electrons.
• Anode:
  • Loses electrons (positive charge).
  • Negative anions move here to lose electrons.
• Electrons from anode return to power supply.
• In electrodes and wires, electrons carry charge. In electrolyte, ions move and carry the charge.

Predicting Products at Electrodes

• Positive ions (cations) move to the cathode.
• Negative ions (anions) move to the anode.
• Electrolyte can be a molten compound or aqueous solution.

Electrolysis of Binary Compounds

• Binary Compound: Composed of two elements.
• Example: Sodium chloride (NaCl)
  • Molten NaCl: Ions are Na+ and Cl-.

Ionic Half Equations and Processes

• Oxidation: Loss of electrons (at anode).
• Reduction: Gain of electrons (at cathode).
• Mnemonic: OIL RIG (Oxidation Is Loss, Reduction Is Gain).
• Example Equations:
  • Anode: 2Cl⁻ → Cl₂ + 2e⁻ (Chloride ions lose electrons to form chlorine gas)
  • Cathode: Na⁺ + e⁻ → Na (Sodium ions gain electrons to form sodium)

Conclusion

• Importance of predicting products and understanding electron flow.
• Encouragement to engage with video content and support creators.