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Experimental data for HCl (Hydrogen chloride)

22 02 02 11 45
Other names
Acide chlorhydrique; Acido cloridrico; Basilin; Chlorohydric acid; Chlorwasserstoff; Hydrochloric Acid; Hydrochloric acid gas; Hydrochloride; Hydrogen chloride; Muriatic acid; NA 1789;
State Conformation
1Σ C*V
Enthalpy of formation (Hfg), Entropy, Integrated heat capacity (0 K to 298.15 K) (HH), Heat Capacity (Cp)
Property Value Uncertainty units Reference Comment
Hfg(298.15K) enthalpy of formation -92.31 0.10 kJ mol-1 CODATA
Hfg(0K) enthalpy of formation -92.13 0.10 kJ mol-1 CODATA
Entropy (298.15K) entropy 186.90 0.00 J K-1 mol-1 CODATA
Integrated Heat Capacity (0 to 298.15K) integrated heat capacity 8.64 0.00 kJ mol-1 CODATA
Heat Capacity (298.15K) heat capacity 29.14   J K-1 mol-1 Gurvich
Information can also be found for this species in the NIST Chemistry Webbook
Vibrational levels (cm-1) vibrations
Mode Number Symmetry Frequency Intensity Comment Description
Fundamental(cm-1) Harmonic(cm-1) Reference (km mol-1) unc. Reference
1 Σ 2886 2991 1979HUB/HER 33.6 3.0 1951Pen/Web:1048

Detailed diatomic data
ωe ωexe ωeye Be αe ZPE reference
2990.925 52.79996 0.21803 10.5933 0.3069985 1483.886 2007Iri:389

vibrational zero-point energy: 1443.0 cm-1 (from fundamental vibrations)
Calculated vibrational frequencies for HCl (Hydrogen chloride).
More spectroscopic constants are available at the NIST Physics Laboratory website:
Rotational Constants (cm-1) rotational constants
See section I.F.4 to change rotational constant units
A B C reference comment
  10.59342   1979HUB/HER

Calculated rotational constants for HCl (Hydrogen chloride).
Product of moments of inertia moments of inertia
1.591331amu Å2   2.642513E-40gm cm2
Geometric Data
picture of Hydrogen chloride

Point Group C∞v

Internal coordinates
distances (r) in Å, angles (a) in degrees, dihedrals (d) in degrees
Description Value unc. Connectivity Reference Comment
Atom 1 Atom 2 Atom 3 Atom 4
rHCl 1.275 0.000 1 2 NISTdiatomic re 1H 35Cl

Atom x (Å) y (Å) z (Å)
Cl1 0.0000 0.0000 0.0000
H2 0.0000 0.0000 1.2746

Atom - Atom Distances bond lengths
Distances in Å
  Cl1 H2
Cl1   1.2746
H2 1.2746  

Calculated geometries for HCl (Hydrogen chloride).

Bond descriptions

Examples: C-C single bond, C=C, double bond, C#C triple bond, C:C aromatic bond
Bond Type Count
H-Cl 1

Atom 1 Atom 2
Cl1 H2
Electronic energy levels (cm-1)
Energy (cm-1) Degeneracy reference description
0 1 1979HUB/HER 1Σ

Ionization Energies (eV)
Ionization Energy I.E. unc. vertical I.E. v.I.E. unc. reference
12.744 0.009     webbook

Proton Affinity (kJ mol-1)
Proton Affinity unc. Product reference comment
556.9   H2Cl+ webbook  
Dipole, Quadrupole and Polarizability
Electric dipole moment dipole
State Config State description Conf description Exp. min. Dipole (Debye) Reference comment Point Group Components
x y z total dipole quadrupole
1 1 1Σ C∞v True       1.093 NISTDiatomic MB μe C∞v 1 1
Experimental dipole measurement abbreviations: MW microwave; DT Dielectric with Temperature variation; DR Indirect (usually an upper limit); MB Molecular beam
Calculated electric dipole moments for HCl (Hydrogen chloride).
Vibration specific dipole moments
Vibrational Quantum numbers Dip x Dip y Dip z Dip total Squib Comment
e       1.093 NISTDiatomic  
0       1.109 NISTDiatomic  
1       1.139 NISTDiatomic  
2       1.168 NISTDiatomic  

Electric quadrupole moment quadrupole
State Config State description Conf description Exp. min. Quadrupole (D Å) Reference comment Point Group Components
xx yy zz dipole quadrupole
1 1 1Σ C∞v True -1.921 -1.921 3.843 1974Hel/Hel(II/6) C∞v 1 1

Calculated electric quadrupole moments for HCl (Hydrogen chloride).
Electric dipole polarizability (Å3) polarizability
alpha unc. Reference
2.515   1997Oln/Can:59

Calculated electric dipole polarizability for HCl (Hydrogen chloride).

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squib reference DOI
1951Pen/Web:1048 SS Penner, D Weber "Quantitative Infrared-Intensity and Line-Width Measurements on HCl, HBr, and NO" Analytical Chemistry 23 (7), 1048, 1951 10.1021/ac60055a041
1974Hel/Hel(II/6) Hellwege, KH and AM Hellwege (eds.). Landolt-Bornstein: Group II: Volume 6 Molecular Constants from Microwave, Molecular Beam, and Electron Spin Resonance Spectroscopy Springer-Verlag. Berlin. 1974. 10.1007/b19951 
1979HUB/HER Huber, K.P.; Herzberg, G., Molecular Spectra and Molecular Structure. IV. Constants of Diatomic Molecules, Van Nostrand Reinhold Co., 1979 10.1007/978-1-4757-0961-2
1997Oln/Can:59 TN Olney, NM Cann, G Cooper, CE Brion, Absolute scale determination for photoabsorption spectra and the calculation of molecular properties using dipole sum-rules, Chem. Phys. 223 (1997) 59-98 10.1016/S0301-0104(97)00145-6
2007Iri:389 KK Irikura "Experimental Vibrational Zero-Point Energies: Diatomic Molecules" J. Phys. Chem. Ref. Data 36(2), 389, 2007 10.1063/1.2436891
CODATA Cox, J.D.; Wagman, D.D.; Medvedev, V.A.CODATA Key Values for Thermodynamics. Hemisphere, New York, 1989 10.1002/bbpc.19900940121
Gurvich Gurvich, L.V.; Veyts, I. V.; Alcock, C. B., Thermodynamic Properties of Individual Substances, Fouth Edition, Hemisphere Pub. Co., New York, 1989  
NISTdiatomic NIST Diatomic Spectral Database ( 10.18434/T4T59X
webbook NIST Chemistry Webbook ( 10.18434/T4D303

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