Question

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

Hint:

Remember: \textbf{A}node attracts \textbf{A}nions (\( Cl^- \rightarrow Cl_2 \)). \textbf{C}athode attracts \textbf{C}ations (\( H^+ \rightarrow H_2 \)).

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).

When electricity is passed through concentrated sodium chloride solution, chemical reactions occur at the anode and cathode, leading to the formation of three important products: chlorine gas, hydrogen gas, and sodium hydroxide.

Overall Chemical Equation: \[ 2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g) \]

Reactions at Electrodes:

At Anode (Positive Electrode):
Chloride ions lose electrons and chlorine gas is formed. \[ 2Cl^- \rightarrow Cl_2 + 2e^- \] Product at anode: Chlorine gas (Cl₂)

At Cathode (Negative Electrode):
Water gains electrons and hydrogen gas is formed along with hydroxide ions. \[ 2H_2O + 2e^- \rightarrow H_2 + 2OH^- \] Product at cathode: Hydrogen gas (H₂)

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

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

Conclusion:
In the chlor–alkali process, electrolysis of brine produces 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.