Hydrogen

• Formula: H₂
• Molecular weight: 2.01588
• IUPAC Standard InChI: InChI=1S/H2/h1H Copy

  
• IUPAC Standard InChIKey: UFHFLCQGNIYNRP-UHFFFAOYSA-N Copy
• CAS Registry Number: 1333-74-0
• Chemical structure:
  This structure is also available as a 2d Mol file or as a computed 3d SD file
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• Isotopologues:
  • tritium
  • deuterium hydride
  • Deuterium
• Other names: Dihydrogen; o-Hydrogen; p-Hydrogen; Molecular hydrogen; H2; UN 1049; UN 1966
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Phase change data
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 100, reactions 101 to 150, reactions 151 to 200, reactions 201 to 250, reactions 251 to 300, reactions 301 to 350, reactions 351 to 400, reactions 401 to 450, reactions 451 to 500, reactions 501 to 550, reactions 551 to 600, reactions 601 to 621
  • Henry's Law data
  • Gas phase ion energetics data
  • Ion clustering data
  • Constants of diatomic molecules
  • Fluid Properties
• Data at other public NIST sites:
  • Electron-Impact Ionization Cross Sections (on physics web site)
  • Gas Phase Kinetics Database
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Gas phase thermochemistry data

Go To: Top, Phase change data, Mass spectrum (electron ionization), References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
    C_p = heat capacity (cal/mol*K)
    H° = standard enthalpy (kcal/mol)
    S° = standard entropy (cal/mol*K)
    t = temperature (K) / 1000.

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Phase change data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
    P = vapor pressure (atm)
    T = temperature (K)

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Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, Phase change data, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Mass spectrum (electron ionization), Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Cox, Wagman, et al., 1984
Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Roder, Childs, et al., 1973
Roder, H.M.; Childs, G.E.; McCarty, R.D.; Angerhofer, P.E., Survey of the Prop. of the Hydrogen Isotopes Below Their Critical Temp, Natl. Bur. Stand. (U. S.), 1973. [all data]

Clusius and Weigand, 1940
Clusius, K.; Weigand, K., Melting Curves of the Gases A, Kr, Xe, CH4, CH3D, CD4, C2H4, C2H6, COS, and PH3 to 200 Atmospheres Pressure. The Chane of Volume on Melting, Z. Phys. Chem., Abt. B, 1940, 46, 1-37. [all data]

Henning and Otto, 1936
Henning, F.; Otto, J., Vapor pressure curves and triple points in the temperature region from 14 to 90 k, Phys. Z., 1936, 37, 633-8. [all data]

Onnes, Crommelin, et al., 1917
Onnes, H.K.; Crommelin, C.-A.; Cath, P.G., Isothermals of di-atomic substances and their binary mixtures. XIX. A preliminary determination of the critical point of hydrogen., Proc. K. Ned. Akad. Wet., 1917, 20, 178-184. [all data]

van Itterbeek, Verbeke, et al., 1964
van Itterbeek, A.; Verbeke, O.; Theewes, F.; Staes, K.; de Boelpaep, J., The Difference in Vapour Pressure Between Normal and Equilibrium Hydrogen. Vapour Pressure of Normal Hydrogen Between 20 ºK and 32 ºK, Physica (Amsterdam), 1964, 30, 6, 1238-1244, https://doi.org/10.1016/0031-8914(64)90114-4 . [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Mass spectrum (electron ionization), References

• Symbols used in this document:
  

  Pc	Critical pressure
  Ptriple	Triple point pressure
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  Tc	Critical temperature
  Ttriple	Triple point temperature
  ρc	Critical density

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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