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
  The 3d structure may be viewed using Java or Javascript.
• 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
  • Henry's Law data
  • Gas phase ion energetics data
  • Ion clustering 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
  • 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
• Options:
  • Switch to SI units

Data at NIST subscription sites:

• NIST / TRC Web Thermo Tables, "lite" edition (thermophysical and thermochemical data)
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Gas phase thermochemistry data

Go To: Top, Phase change data, Henry's Law data, Gas phase ion energetics data, Ion clustering 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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View table.

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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Henry's Law 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 by: Rolf Sander

Henry's Law constant (water solution)

k_H(T) = k°_H exp(d(ln(k_H))/d(1/T) ((1/T) - 1/(298.15 K)))
k°_H = Henry's law constant for solubility in water at 298.15 K (mol/(kg*bar))
d(ln(k_H))/d(1/T) = Temperature dependence constant (K)

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law data, Ion clustering 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.

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

View reactions leading to H₂⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

 +  =

By formula: H^- + H⁺ = H₂

Ion clustering 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 by: Michael M. Meot-Ner (Mautner) and Sharon G. Lias

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

Ar⁺ +  = (Ar⁺ • )

By formula: Ar⁺ + H₂ = (Ar⁺ • H₂)

 +  = ( • )

By formula: CHO⁺ + H₂ = (CHO⁺ • H₂)

CH₅⁺ +  = (CH₅⁺ • )

By formula: CH₅⁺ + H₂ = (CH₅⁺ • H₂)

(CH₅⁺ • ) +  = (CH₅⁺ • 2)

By formula: (CH₅⁺ • H₂) + H₂ = (CH₅⁺ • 2H₂)

(CH₅⁺ • 2) +  = (CH₅⁺ • 3)

By formula: (CH₅⁺ • 2H₂) + H₂ = (CH₅⁺ • 3H₂)

(CH₅⁺ • 3) +  = (CH₅⁺ • 4)

By formula: (CH₅⁺ • 3H₂) + H₂ = (CH₅⁺ • 4H₂)

C₃H₇⁺ +  = (C₃H₇⁺ • )

By formula: C₃H₇⁺ + H₂ = (C₃H₇⁺ • H₂)

Free energy of reaction

( • ) +  = ( •  • )

By formula: (Co⁺ • CH₄) + H₂ = (Co⁺ • H₂ • CH₄)

Enthalpy of reaction

( • ) +  = ( •  • )

By formula: (Co⁺ • H₂O) + H₂ = (Co⁺ • H₂ • H₂O)

Enthalpy of reaction

 +  = ( • )

By formula: Co⁺ + H₂ = (Co⁺ • H₂)

Enthalpy of reaction

( • ) +  = ( • 2)

By formula: (Co⁺ • H₂) + H₂ = (Co⁺ • 2H₂)

( • 2) +  = ( • 3)

By formula: (Co⁺ • 2H₂) + H₂ = (Co⁺ • 3H₂)

( • 3) +  = ( • 4)

By formula: (Co⁺ • 3H₂) + H₂ = (Co⁺ • 4H₂)

( • 4) +  = ( • 5)

By formula: (Co⁺ • 4H₂) + H₂ = (Co⁺ • 5H₂)

( • 5) +  = ( • 6)

By formula: (Co⁺ • 5H₂) + H₂ = (Co⁺ • 6H₂)

( • 6) +  = ( • 7)

By formula: (Co⁺ • 6H₂) + H₂ = (Co⁺ • 7H₂)

 +  = ( • )

By formula: Fe⁺ + H₂ = (Fe⁺ • H₂)

( • ) +  = ( • 2)

By formula: (Fe⁺ • H₂) + H₂ = (Fe⁺ • 2H₂)

( • 2) +  = ( • 3)

By formula: (Fe⁺ • 2H₂) + H₂ = (Fe⁺ • 3H₂)

( • 3) +  = ( • 4)

By formula: (Fe⁺ • 3H₂) + H₂ = (Fe⁺ • 4H₂)

( • 4) +  = ( • 5)

By formula: (Fe⁺ • 4H₂) + H₂ = (Fe⁺ • 5H₂)

( • 5) +  = ( • 6)

By formula: (Fe⁺ • 5H₂) + H₂ = (Fe⁺ • 6H₂)

HN₂⁺ +  = (HN₂⁺ • )

By formula: HN₂⁺ + H₂ = (HN₂⁺ • H₂)

(HN₂⁺ • ) +  = (HN₂⁺ • 2)

By formula: (HN₂⁺ • H₂) + H₂ = (HN₂⁺ • 2H₂)

 +  = ( • )

By formula: HO^- + H₂ = (HO^- • H₂)

HO₂⁺ +  = (HO₂⁺ • )

By formula: HO₂⁺ + H₂ = (HO₂⁺ • H₂)

(HO₂⁺ • ) +  = (HO₂⁺ •  • )

By formula: (HO₂⁺ • O₂) + H₂ = (HO₂⁺ • H₂ • O₂)

H₃⁺ +  = (H₃⁺ • )

By formula: H₃⁺ + H₂ = (H₃⁺ • H₂)

(H₃⁺ • ) +  = (H₃⁺ • 2)

By formula: (H₃⁺ • H₂) + H₂ = (H₃⁺ • 2H₂)

(H₃⁺ • 2) +  = (H₃⁺ • 3)

By formula: (H₃⁺ • 2H₂) + H₂ = (H₃⁺ • 3H₂)

(H₃⁺ • 3) +  = (H₃⁺ • 4)

By formula: (H₃⁺ • 3H₂) + H₂ = (H₃⁺ • 4H₂)

(H₃⁺ • 4) +  = (H₃⁺ • 5)

By formula: (H₃⁺ • 4H₂) + H₂ = (H₃⁺ • 5H₂)

(H₃⁺ • 5) +  = (H₃⁺ • 6)

By formula: (H₃⁺ • 5H₂) + H₂ = (H₃⁺ • 6H₂)

(H₃⁺ • 6) +  = (H₃⁺ • 7)

By formula: (H₃⁺ • 6H₂) + H₂ = (H₃⁺ • 7H₂)

(H₃⁺ • 7) +  = (H₃⁺ • 8)

By formula: (H₃⁺ • 7H₂) + H₂ = (H₃⁺ • 8H₂)

(H₃⁺ • 8) +  = (H₃⁺ • 9)

By formula: (H₃⁺ • 8H₂) + H₂ = (H₃⁺ • 9H₂)

 +  = ( • )

By formula: H₃O⁺ + H₂ = (H₃O⁺ • H₂)

 +  = ( • )

By formula: K⁺ + H₂ = (K⁺ • H₂)

( • ) +  = ( • 2)

By formula: (K⁺ • H₂) + H₂ = (K⁺ • 2H₂)

 +  = ( • )

By formula: Li⁺ + H₂ = (Li⁺ • H₂)

 +  = ( • )

By formula: Na⁺ + H₂ = (Na⁺ • H₂)

( • ) +  = ( • 2)

By formula: (Na⁺ • H₂) + H₂ = (Na⁺ • 2H₂)

Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law data, Gas phase ion energetics data, Ion clustering 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, Henry's Law data, Gas phase ion energetics data, Ion clustering 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.

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Hiraoka and Kebarle, 1975, 2
Hiraoka, K.; Kebarle, P., A Determination of the Stabilities of H5+, H7+, H9+, and H11+ from Measurement of the Gas Phase Ion Equilibria Hn+ + H2 = H(n + 2)+ (n = 3, 5, 7, 9), J. Chem. Phys., 1975, 62, 6, 2267, https://doi.org/10.1063/1.430751 . [all data]

Bennett and Field, 1972
Bennett, S.L.; Field, F.H., Reversible Reactions of Gaseous Ions. VII. The Hydrogen System, J. Am. Chem. Soc., 1972, 94, 25, 8669, https://doi.org/10.1021/ja00780a003 . [all data]

Okumura, Yeh, et al., 1990
Okumura, M.; Yeh, L.I.; Myers, J.D.; Lee, Y.T., Infrared Spectra of the Solvated Hydronium Ion: Vibrational Predissociation Spectroscopy of Mass-Selected H3O+.(H2O)n.(H2)m, J. Phys. Chem., 1990, 94, 9, 3416, https://doi.org/10.1021/j100372a014 . [all data]

Bushnell, Kemper, et al., 1994
Bushnell, J.E.; Kemper, P.R.; Bowers, M.T., Na+/K+(H2)1,2 clusters: experiment, J. Phys. Chem., 1994, 98, 8, 2044, https://doi.org/10.1021/j100059a011 . [all data]

Wu, 1979
Wu, C.H., Binding Energies of LiH2 and LiH2+ and the Ionization Potential of LiH2, J. Chem. Phys., 1979, 71, 2, 783, https://doi.org/10.1063/1.438367 . [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law data, Gas phase ion energetics data, Ion clustering data, Mass spectrum (electron ionization), References

• Symbols used in this document:
  

  AE	Appearance energy
  IE (evaluated)	Recommended ionization energy
  Pc	Critical pressure
  Ptriple	Triple point pressure
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  T	Temperature
  Tc	Critical temperature
  Ttriple	Triple point temperature
  d(ln(kH))/d(1/T)	Temperature dependence parameter for Henry's Law constant
  k°H	Henry's Law constant at 298.15K
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔrS°	Entropy of reaction at standard conditions
  ρc	Critical density

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