Question

Explain chlor-alkali process with chemical equation. Name the products formed at anode and cathode.

Hint:

Chlor-alkali process: Electrolysis of brine \(\Rightarrow\) NaOH + Cl₂ + H₂. Anode (+): Cl⁻ oxidized to Cl₂ gas. Cathode (-): H₂O reduced to H₂ gas and OH⁻ (forms NaOH). Products: Chlorine (anode), Hydrogen (cathode), Sodium hydroxide (in solution).

Answer 1

Chlor-Alkali Process:

The chlor-alkali process is the industrial process used for the electrolysis of an aqueous solution of sodium chloride (brine). It is called “chlor-alkali” because it produces chlorine (chlor) and an alkali (sodium hydroxide).

In this process, electricity is passed through concentrated sodium chloride solution. As a result, chemical reactions occur at the anode and cathode, producing important industrial chemicals.

Chemical Equation for the Overall Reaction:

2NaCl (aq) + 2H₂O (l) → 2NaOH (aq) + Cl₂ (g) + H₂ (g)

Products Formed at Each Electrode:

At Anode (Positive Electrode):
Chlorine gas (Cl₂) is produced.

Anode reaction:
2Cl⁻ → Cl₂ + 2e⁻

At Cathode (Negative Electrode):
Hydrogen gas (H₂) is produced.

Cathode reaction:
2H₂O + 2e⁻ → H₂ + 2OH⁻

The sodium ions (Na⁺) combine with hydroxide ions (OH⁻) to form sodium hydroxide (NaOH) solution.

Uses of the Products:

– Chlorine gas: Used in making PVC, disinfectants, bleaching powder, and water purification.
– Hydrogen gas: Used in making ammonia and as a fuel.
– Sodium hydroxide: Used in soap making, paper industry, and textile industry.

Conclusion:
The chlor-alkali process involves electrolysis of brine to produce chlorine gas at the anode, hydrogen gas at the cathode, and sodium hydroxide in solution. It is an important industrial process for manufacturing essential chemicals.