Advanced Topic 577 of 1102 Acids, Bases & Electrochemistry
Chlor-Alkali Process
Electrolysis of brine produces chlorine, hydrogen and sodium hydroxide.
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In-depth explanation of Chlor-Alkali Process
The chlor-alkali process electrolyzes concentrated brine to produce chlorine, hydrogen and sodium hydroxide, three of the most important industrial chemicals. In modern membrane cells chlorine forms at the anode while hydrogen and hydroxide form at the cathode, and a membrane keeps the two products apart. Separation prevents the products from recombining into hypochlorite and yields pure sodium hydroxide. Chlorine is used in water treatment and plastics, hydrogen in ammonia production, and sodium hydroxide in paper and soap manufacture. The process consumes large amounts of electricity and is a major use of industrial electrolysis.
Going deeper: Chlor-Alkali Process
Key ideas: Electrolysis of brine (NaCl solution) gives Cl2 at the anode, H2 and NaOH at the cathode: 2NaCl + 2H2O giving Cl2 + H2 + 2NaOH. Three cell types: membrane (modern, ion-exchange membrane), diaphragm and mercury (being phased out). Mass ratio is about 1.1 t of Cl2 per 1.0 t of NaOH.
Common mistakes and connections: Mistakes: expecting Na metal, and ignoring the need to keep Cl2 from mixing with NaOH (forms bleach NaOCl). The membrane passes Na+ but blocks Cl- and OH-, giving high purity. Chlorine is an anode product despite water oxidation being thermodynamically easier, because of overpotential.
Visualization of Chlor-Alkali Process
The chlor-alkali cell makes Cl2 at the anode and H2 plus NaOH at the cathode, with a membrane keeping the products from reacting. The interactive lesson shows this as a live animation or chart.
Worked example and use case
The overall reaction is 2NaCl + 2H2O -> Cl2 + H2 + 2NaOH.
Frequently asked questions about Chlor-Alkali Process
What is Chlor-Alkali Process?
Electrolysis of brine produces chlorine, hydrogen and sodium hydroxide.
Is Chlor-Alkali Process a beginner, intermediate or advanced topic?
Chlor-Alkali Process is a advanced topic in Acids, Bases & Electrochemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Chlor-Alkali Process?
Study these earlier topics in Acids, Bases & Electrochemistry first: Electroplating, Electrorefining, Hall-Heroult Process.
What comes after Chlor-Alkali Process?
The next topics in Acids, Bases & Electrochemistry are Dry Cell and Alkaline Battery.
Can I practise Chlor-Alkali Process with quizzes?
Yes. The interactive lesson includes a self-check question on Chlor-Alkali Process, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where Chlor-Alkali Process fits in Acids, Bases & Electrochemistry
Chlor-Alkali Process is topic 67 of 105 in Acids, Bases & Electrochemistry.