Electrolysis of Sodium Chloride

What is Electrolysis?

• Definition: Process of using electricity to drive a chemical reaction that would not occur spontaneously.

Key Components

• Electrolyte: A substance that produces an electrically conducting solution when dissolved in a polar solvent like water.
  • Example discussed: Sodium chloride (NaCl)
• Anode vs Cathode: Two types of electrodes used in electrolysis.
  • Anode: Positive electrode where oxidation occurs (loss of electrons).
  • Cathode: Negative electrode where reduction occurs (gain of electrons).

Types of Reactions

• Spontaneous Reactions: Reactions that occur naturally without external energy.
  • Example: Conversion of zinc atoms to Zn²⁺ by losing electrons.
• Non-Spontaneous Reactions: Reactions that require external energy (electricity) to occur.
  • Example discussed: Electrolysis of NaCl.

Oxidation and Reduction

• Oxidation: Loss of electrons.
  • Example: Cl₂ gaining electrons to form Cl⁻ (chlorine gas is reduced to chloride ions).
• Reduction: Gain of electrons.
  • Example: Na⁺ ions gaining electrons to form Na (sodium metal is formed at the cathode).

Mechanism of Sodium Chloride Electrolysis

• Setup: Electrolytic Cell
  • Sodium chloride is melted to form liquid electrolyte.
  • Electrodes are inserted (anode connected to the positive terminal and cathode to the negative terminal of the battery).
• Process:
  1. At Cathode (Reduction): Sodium ions (Na⁺) gain electrons to form sodium metal (Na).
     • Equation: Na⁺ + e⁻ → Na
  2. At Anode (Oxidation): Chloride ions (Cl⁻) lose electrons to form chlorine gas (Cl₂).
     • Equation: 2Cl⁻ - 2e⁻ → Cl₂↑
  3. Overall Reaction: ClNa → Na (at cathode) + Cl₂ (at anode)

Applications of Electrolysis

• Production of Elements: Sodium metal, chlorine gas.
• Industrial Use: Electroplating, extraction of metals.

Differences Between Electrolytic and Spontaneous Reactions

• Electrolytic Reaction: Requires external electric energy.
• Spontaneous Reaction: Occurs naturally without external energy.

Important Points to Remember

• Electrolyte's role: Enables flow of electric current by ion movement.
• Anode vs Cathode role: Anode for oxidation, cathode for reduction.
• Balancing Reactions: Number of electrons lost must equal the number of electrons gained.
• Electrolysis is used for driving non-spontaneous reactions using electrical energy.