Describe the chlor-alkali process. Write the chemical equation involved and name the products formed at each electrode.
Generated by claude-sonnet-4-6 · 2026-06-17 12:37 · grounding rag
Model Answer
Chlor-alkali process: When electricity is passed through an aqueous solution of sodium chloride (brine), it decomposes. This process is called the chlor-alkali process (chlor = chlorine; alkali = sodium hydroxide).
Chemical equation:
$$2\text{NaCl(aq)} + 2\text{H}_2\text{O(l)} \rightarrow 2\text{NaOH(aq)} + \text{Cl}_2\text{(g)} + \text{H}_2\text{(g)}$$
Products at each electrode:
- Anode (+): Chlorine gas (Cl₂)
- Cathode (−): Hydrogen gas (H₂); sodium hydroxide (NaOH) solution is also formed near the cathode.
Source: Chapter 2, Section 2.4.3
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Explanation
- The name "chlor-alkali" must be explained (1 mark).
- The balanced equation is essential (1 mark).
- Products at each electrode must be stated clearly — examiners specifically check anode → Cl₂ and cathode → H₂ + NaOH (1 mark).
- Do not confuse: NaOH forms near the cathode, not directly at it. All three points are directly from the textbook passage.