Intermediate Topic 626 of 1102 Inorganic Chemistry
Sodium Hydroxide Production
Made mainly via the chlor-alkali electrolysis of brine.
In-depth explanation of Sodium Hydroxide Production
Sodium hydroxide, also called caustic soda, is made mainly by the chlor-alkali process, the electrolysis of concentrated brine. In a membrane cell the overall reaction is 2NaCl + 2H2O giving 2NaOH + H2 + Cl2, and a membrane keeps the chlorine and the sodium hydroxide apart. NaOH is a strong, caustic base that dissolves in water with a large release of heat, so the solid must be added slowly to water. It absorbs moisture from air and attacks skin, glass and some metals. Its main uses are in soap and detergent manufacture, paper pulping, alumina refining and drain cleaners.
Going deeper: Sodium Hydroxide Production
Key ideas: Chlor-alkali process: 2NaCl + 2H2O gives 2NaOH + Cl2 + H2 on electrolysis. Cl2 forms at the anode, H2 and NaOH at the cathode. Three cell types: mercury, diaphragm, and the modern membrane cell, which gives the purest NaOH with low energy. A membrane cell passes only Na+ and water. Current needed: 96485 C gives 1 mol of NaOH per mole of electrons.
Common mistakes and connections: Students think Na metal forms at the cathode, but in aqueous solution water is reduced preferentially. The products must be kept apart, since Cl2 with NaOH forms hypochlorite and chlorate. Mercury cells were phased out because of mercury pollution. Links to electrolysis, Faraday laws and bleach manufacture.
Visualization of Sodium Hydroxide Production
Membrane chlor-alkali cell: chlorine forms at the anode, hydrogen and hydroxide at the cathode, and the membrane keeps the products apart. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Dissolving 40 g of NaOH, one mole, in water to make one litre gives a solution with a pH close to 14.
Frequently asked questions about Sodium Hydroxide Production
What is Sodium Hydroxide Production?
Made mainly via the chlor-alkali electrolysis of brine.
Is Sodium Hydroxide Production a beginner, intermediate or advanced topic?
Sodium Hydroxide Production is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Sodium Hydroxide Production?
Study these earlier topics in Inorganic Chemistry first: Reaction of Alkali Metals with Water, Flame Tests, Sodium Chemistry.
What comes after Sodium Hydroxide Production?
The next topics in Inorganic Chemistry are Solvay Process and Alkaline Earth Metals.
Can I practise Sodium Hydroxide Production with quizzes?
Yes. The interactive lesson includes a self-check question on Sodium Hydroxide Production, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Sodium Hydroxide Production fits in Inorganic Chemistry
Sodium Hydroxide Production is topic 11 of 113 in Inorganic Chemistry.