Electrolysis

What is Electrolysis?

Electrolysis is the process in which electrical energy is used to drive a non-spontaneous chemical reaction. It involves the passage of direct electric current through an electrolyte, causing the movement of ions and chemical changes at the electrodes.

This process is widely used in industries for electroplating, purification of metals, and extraction of reactive metals.

Key Terms in Electrolysis

• Electrolyte: A substance that conducts electricity when molten or dissolved in water, breaking down into ions.
• Electrode: Conductors through which electricity enters or leaves the electrolyte.
• Anode: The positively charged electrode where oxidation occurs.
• Cathode: The negatively charged electrode where reduction occurs.

Mechanism of Electrolysis

During electrolysis:

• Cations (positive ions) move toward the cathode and gain electrons (reduction).
• Anions (negative ions) move toward the anode and lose electrons (oxidation).

Example: Electrolysis of molten NaCl

• At Cathode: Na⁺ + e⁻ → Na (Reduction)
• At Anode: 2Cl⁻ → Cl₂ + 2e⁻ (Oxidation)

Industrial Applications

• Electroplating: Coating of a metal with a thin layer of another metal (e.g., silver-plated jewelry).
• Electrorefining: Purification of metals such as copper.
• Electrolysis of water: Produces hydrogen and oxygen gases.
• Metal Extraction: Used to extract reactive metals like aluminum from their ores.

Faraday’s Laws of Electrolysis

• First Law: The mass of a substance deposited or liberated at an electrode is directly proportional to the quantity of electricity passed through the electrolyte.
• Second Law: When the same amount of electricity is passed through different electrolytes, the mass of substances deposited is proportional to their equivalent weights.

Previous Year Questions

• RRB JE 2017: What is the product formed at the cathode during the electrolysis of molten NaCl?
• Sodium metal (Na)
• SSC JE 2018: Which gas is released at the anode during electrolysis of water?
• Oxygen (O₂)
• HSSC 2020: Which electrode does oxidation take place in electrolysis?
• Anode

Conclusion

Electrolysis is a vital chemical process with wide-ranging applications in industries and laboratories. It helps us extract, refine, and coat metals, and even split compounds like water into useful gases. Understanding electrolysis is essential for mastering electrochemistry in science and engineering domains.