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II.A.1. (XV.A.)

Listing of experimental data for HI (Hydrogen iodide)

Other names
Hydriodic acid; Hydroiodic acid; hydrogen iodide;
InChI=1/HI/h1H I hydrogen iodide
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 26.50 0.10 kJ mol-1 CODATA
Hfg(0K) enthalpy of formation 28.68 0.10 kJ mol-1 CODATA
Entropy (298.15K) entropy 206.59   J K-1 mol-1 webbook
Integrated Heat Capacity (0 to 298.15K) integrated heat capacity 8.66   kJ mol-1 Gurvich
Heat Capacity (298.15K) heat capacity 29.16   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 (cm-1) Frequency Reference Intensity (km mol-1) Int. unc. Intensity Reference Comment
1 Σ 2309 webbook      

vibrational zero-point energy: 1154.5 cm-1
Calculated vibrational frequencies for HI (Hydrogen iodide).
Rotational Constants (cm-1) rotational constants
See section I.F.4 to change rotational constant units
A B C reference comment
  6.42637 6.42637 webbook

Calculated rotational constants for HI (Hydrogen iodide).

Product of moments of inertia moments of inertia
2.623199amu Å2   4.355992E-40gm cm2

Geometric Data
picture of Hydrogen iodide

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
rHI 1.609 0.000 1 2 NISTdiatomic re

Atom x (Å) y (Å) z (Å)
I1 0.0000 0.0000 0.0000
H2 0.0000 0.0000 1.6092

Atom - Atom Distances bond lengths
Distances in Å
  I1 H2
I1   1.6092
H2 1.6092  

Calculated geometries for HI (Hydrogen iodide).

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

Atom 1 Atom 2
I1 H2

Electronic energy levels (cm-1)
Energy (cm-1) Degeneracy reference description
0 1   1Σ

Ionization Energies (eV)
Ionization Energy I.E. unc. vertical I.E. v.I.E. unc. reference
10.386 0.001     webbook

Dipole, Quadrupole and Polarizability
Electric dipole moment dipole
Dipole (Debye) Reference comment
0.448 webbook  

Calculated electric dipole moments for HI (Hydrogen iodide).
Electric quadrupole moment quadrupole
Calculated electric quadrupole moments for HI (Hydrogen iodide).

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squib reference DOI
CODATA Cox, J.D.; Wagman, D.D.; Medvedev, V.A.CODATA Key Values for Thermodynamics. Hemisphere, New York, 1989  
Gurvich Gurvich, L.V.; Veyts, I. V.; Alcock, C. B., Thermodynamic Properties of Individual Substances, Fouth Edition, Hemisphere Pub. Co., New York, 1989 10.1351/pac198961061027
NISTdiatomic NIST Diatomic Spectral Database (  
webbook NIST Chemistry Webbook (  

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