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HCl

Hydrogen chloride
Skeletal formula of hydrogen chloride with a dimension
Space-filling model of hydrogen chloride with atom symbols
Names
IUPAC name
Hydrogen chloride
Other names
Hydrochloric acid gas
Hydrochloride
Identifiers
7647-01-0 YesY
3D model (Jmol) Interactive image
1098214
ChEBI CHEBI:17883 YesY
ChEMBL ChEMBL1231821 N
ChemSpider 307 YesY
ECHA InfoCard 100.028.723
EC Number 231-595-7
322
KEGG D02057 YesY
MeSH Hydrochloric+acid
RTECS number MW4025000
UNII QTT17582CB YesY
UN number 1050
Properties
ClH
Molar mass 36.46 g·mol−1
Appearance Colorless gas
Odor pungent
Density 1.49 g L−1
Melting point −114.22 °C (−173.60 °F; 158.93 K)
Boiling point −85.05 °C (−121.09 °F; 188.10 K)
823 g/L (0 °C)
720 g/L (20 °C)
561 g/L (60 °C)
Solubility soluble in methanol, ethanol, ether
Vapor pressure 4352 kPa (at 21.1 °C)
Acidity (pKa) -3.0; -5.9 (±0.4)
Basicity (pKb) 17.0
1.0004456 (gas)
1.254 (liquid)
Viscosity 0.311 cP (−100 °C)
Structure
linear
1.05 D
Thermochemistry
0.7981 J K−1 g−1
186.902 J K−1 mol−1
 –92.31 kJ mol−1
 –95.31 kJ mol−1
Pharmacology
A09AB03 (WHO) B05XA13 (WHO)
Hazards
Safety data sheet JT Baker MSDS
GHS pictograms The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H280, H314, H331
P261, P280, P305+351+338, P310, P410+403
Toxic T Corrosive C
R-phrases R23, R35
S-phrases (S1/2), S9, S26, S36/37/39, S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazard ACID: Acid.NFPA 704 four-colored diamond
Lethal dose or concentration (LD, LC):
LD50 (median dose)
238 mg/kg (rat, oral)
3124 ppm (rat, 1 hr)
1108 ppm (mouse, 1 hr)
1300 ppm (human, 30 min)
4416 ppm (rabbit, 30 min)
4416 ppm (guinea pig, 30 min)
3000 ppm (human, 5 min)
US health exposure limits (NIOSH):
PEL (Permissible)
C 5 ppm (7 mg/m3)
REL (Recommended)
C 5 ppm (7 mg/m3)
IDLH (Immediate danger)
50 ppm
Related compounds
Related compounds
Hydrogen fluoride
Hydrogen bromide
Hydrogen iodide
Hydrogen astatide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

The compound hydrogen chloride has the chemical formula HCl and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry. Hydrochloric acid, the aqueous solution of hydrogen chloride, is also commonly given the formula HCl.

Hydrogen chloride is a diatomic molecule, consisting of a hydrogen atom H and a chlorine atom Cl connected by a covalent single bond. Since the chlorine atom is much more electronegative than the hydrogen atom, the covalent bond between the two atoms is quite polar. Consequently, the molecule has a large dipole moment with a negative partial charge (δ−) at the chlorine atom and a positive partial charge (δ+) at the hydrogen atom. In part because of its high polarity, HCl is very soluble in water (and in other polar solvents).

Upon contact, H2O and HCl combine to form hydronium cations H3O+ and chloride anions Cl through a reversible chemical reaction:


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