What is the chlor-alkali process? Write the equation, name the product at each electrode, and give one use of each product.

1. 1 · Define in one line. The chlor-alkali process is the electrolysis of brine (sodium chloride solution) to give chlorine, hydrogen and sodium hydroxide.
2. 2 · Write the equation. 2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂(g) + H₂(g)
3. 3 · Draw the cell. Draw a tank of brine with two electrodes joined to a battery. Label: anode (+) with chlorine gas rising, cathode (−) with hydrogen gas rising, sodium hydroxide solution near the cathode, brine.
4. 4 · Give the uses.
   • Chlorine: water treatment, swimming pools, PVC, pesticides, bleaching powder.
   • Hydrogen: fuels, margarine, ammonia for fertilisers.
   • Sodium hydroxide: soaps and detergents, paper, de-greasing metals, artificial fibres.
5. 5 · Link to real life. The bleaching powder used to clean village wells is made from chlorine from this process.
6. 6 · Close in one line. So one cheap raw material, common salt, gives three useful chemicals.

Scoring tip: Get the electrodes right: chlorine at the anode, hydrogen at the cathode. Mixing them up is the most common mistake.