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How is chlorine used in the production of hydrochloric acid?

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A labeled diagram of the chlorine element from the periodic table shows its atomic number 17, symbol Cl, electron configuration, and atomic weight range. The box is shaded green to indicate chlorine is a halogen, with icons for orthorhombic crystal structure, gas state at room temperature, and strong acidity. A key explains the icons and colors used.
chlorine Properties of chlorine.

Chlorine is a fundamental component in the production of hydrochloric acid, which is created by dissolving gaseous hydrogen chloride in water.1

Chlorine gas (Cl2) is used to produce hydrogen chloride through several methods:

  • Direct Combination: Chlorine gas can be reacted directly with hydrogen gas (H2). This reaction, represented by the equation H2+Cl2→2HCl, is rapid at temperatures above 250 °C and releases heat.12
  • By-product of Chlorination: Hydrogen chloride is frequently generated as a by-product during the industrial chlorination of various organic substances, such as methane or benzene.1
  • Chemical Reactions: Chlorine-containing compounds, such as phosphorus trichloride or thionyl chloride, can react with water to produce hydrogen chloride. Additionally, hydrogen gas can reduce certain metal chlorides (such as palladium chloride) to form hydrogen chloride.12

Once the hydrogen chloride gas is produced, it is dissolved in water to form the final hydrochloric acid solution.1