Hydrogen chloride

Structural formula
General
Surname Hydrogen chloride
other names
• Hydrochloric acid anhydrous
• Hydrogen chloride ( IUPAC )
• Hydrochloric acid gas
• Hydrogen chloride
• Chlorane
• HYDROCHLORIC ACID ( INCI )
Molecular formula HCl
Brief description

colorless, pungent smelling gas

External identifiers / databases
 CAS number 7647-01-0 EC number 231-595-7 ECHA InfoCard 100.028.723 PubChem 313 Wikidata Q211086
properties
Molar mass 36.46 g mol −1
Physical state

gaseous

density

1.64 kg m −3 (gas density, 0 ° C)

Melting point

−114.8 ° C

boiling point

−85.0 ° C

Vapor pressure

4.26 M Pa (20 ° C)

pK s value

−6.2

solubility

easily in water (720 g l −1 at 20 ° C)

Dipole moment

1.1086 (3) D (3.698 · 10 −30  C  ·  m )

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary

danger

H and P phrases H: 331-314-280
EUH: 071
P: 260-280-304 + 340-303 + 361 + 353-305 + 351 + 338-315-405-403
MAK

DFG / Switzerland: 2 ml m −3 or 3 mg m −3

Thermodynamic properties
ΔH f 0

−92.3 kJ / mol

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Hydrogen chloride ( molecular formula HCl, systematically also referred to as hydrogen chloride or hydrogen chloride ) is a colorless, pungent smelling gas that dissolves very easily in water . Aqueous solutions of hydrogen chloride are called hydrochloric acid or hydrochloric acid. If you inhale the gas, hydrochloric acid is produced in the lungs, which leads to severe burns, since hydrochloric acid is a very strong acid .

He was portrayed by Humphry Davy in 1808.

Extraction and presentation

Hydrogen chloride is produced in the laboratory from concentrated sulfuric acid and sodium chloride :

${\ displaystyle \ mathrm {2 \; NaCl + H_ {2} SO_ {4} \ rightarrow Na_ {2} SO_ {4} +2 \; HCl}}$
Sodium chloride and sulfuric acid react to form sodium sulfate and hydrogen chloride

Instead of using sulfuric acid, sodium hydrogen sulfate can also be used. For this purpose, a mixture of sodium chloride and sodium hydrogen sulfate is heated dry. In order to keep the reaction going, the resulting hydrogen chloride gas has to be removed.

In the chemical industry, hydrogen chloride occurs mainly as a by-product in the chlorination of organic compounds or is obtained with the chlorine- explosive gas reaction (ignition of a mixture of hydrogen and chlorine, for example by exposure).

${\ displaystyle \ mathrm {H_ {2} + Cl_ {2} \ rightarrow 2 \; HCl}}$
Hydrogen and chlorine react to form hydrogen chloride

In the photochlorination or sulfochlorination of hydrocarbons, hydrogen chloride is produced as a by-product:

properties

The systematic designation hydrogen chloride uses the syllable chloride to express that the chlorine atom in the molecular compound carries a negative partial charge , similar to chloride ions , which have a negative ionic charge .

Hydrogen chloride has a slightly higher density than air . In one liter of water , 520 l dissolve at 0  ° C when heated, which corresponds to 850 g of HCl gas. At 20 ° C, 442 liters of hydrogen chloride dissolve in one liter of water. In humid air, HCl gas forms a mist of fine hydrochloric acid droplets.

Its specific heat capacity c p is 799 J / (kg K).

Biological importance

Hydrogen chloride, in the form of hydrochloric acid, is a component of the gastric juice of omnivorous animals and also causes food to be denatured in the human stomach .

use

In addition to its diverse uses as an acid, pure hydrogen chloride is also used as a chlorinating agent in the oxychlorination of ethene to vinyl chloride .

safety instructions

Hydrogen chloride is corrosive and toxic in high concentrations. However, poisoning is very rare. Inhalation can cause irritation and chemical burns to the mucous membranes and the respiratory tract, which can lead to acute bronchitis or pneumonia . If it comes into contact with skin and clothing, the acid can be washed out thoroughly and completely with water.