Water

• Formula: H₂O
• Molecular weight: 18.0153
• IUPAC Standard InChI: InChI=1S/H2O/h1H2 Copy

  
• IUPAC Standard InChIKey: XLYOFNOQVPJJNP-UHFFFAOYSA-N Copy
• CAS Registry Number: 7732-18-5
• 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:
  • Deuterium oxide
  • Water-t
  • Water-¹⁸O
  • Water-d
  • Water-t₂
  • Deuterium oxide
• Other names: Water vapor; Distilled water; Ice; H2O; Dihydrogen oxide; steam; Tritiotope
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Condensed phase thermochemistry data
  • Phase change data
  • Gas phase ion energetics data
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Gas phase thermochemistry data
  • 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 650, reactions 651 to 700, reactions 701 to 750, reactions 751 to 800, reactions 801 to 850, reactions 851 to 900, reactions 901 to 950, reactions 951 to 1000, reactions 1001 to 1050, reactions 1051 to 1100, reactions 1101 to 1150, reactions 1151 to 1200, reactions 1201 to 1250, reactions 1251 to 1300, reactions 1301 to 1350, reactions 1351 to 1360
  • Ion clustering data
  • IR Spectrum
  • Vibrational and/or electronic energy levels
  • Gas Chromatography
  • Fluid Properties
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Electron-Impact Ionization Cross Sections (on physics web site)
  • Gas Phase Kinetics Database
  • Reference simulation: SPC/E Water
  • X-ray Photoelectron Spectroscopy Database, version 5.0
• Options:
  • Switch to calorie-based units

Data at NIST subscription sites:

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

NIST subscription sites provide data under the NIST Standard Reference Data Program, but require an annual fee to access. The purpose of the fee is to recover costs associated with the development of data collections included in such sites. Your institution may already be a subscriber. Follow the links above to find out more about the data in these sites and their terms of usage.

Condensed phase thermochemistry data

Go To: Top, Phase change data, Gas phase ion energetics 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.

Liquid 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 (J/mol*K)
    H° = standard enthalpy (kJ/mol)
    S° = standard entropy (J/mol*K)
    t = temperature (K) / 1000.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Phase change data

Go To: Top, Condensed phase thermochemistry data, Gas phase ion energetics 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 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 (bar)
    T = temperature (K)

View plot Requires a JavaScript / HTML 5 canvas capable browser.

Gas phase ion energetics data

Go To: Top, Condensed phase thermochemistry data, 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.

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 H₂O⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

HO^- +  =

By formula: HO^- + H⁺ = H₂O

Mass spectrum (electron ionization)

Go To: Top, Condensed phase thermochemistry data, Phase change data, Gas phase ion energetics 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

Notice: This spectrum may be better viewed with a Javascript and HTML 5 enabled browser.

For Zoom

1.) Enter the desired X axis range (e.g., 100, 200)

2.) Check here for automatic Y scaling

3.) Press here to zoom

Additional Data

References

Go To: Top, Condensed phase thermochemistry data, Phase change data, Gas phase ion energetics 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]

Sato, Watanabe, et al., 1991
Sato, H.; Watanabe, K.; Levelt Sengers, J.M.H.; Gallagher, J.S.; Hill, P.G.; Straub, J.; Wagner, W., Sixteen Thousand Evaluated Experimental Thermodynamic Property Data for Water and Steam, J. Phys. Chem. Ref. Data, 1991, 20, 1023. [all data]

Brunner, 1990
Brunner, E., Fluid Mixtures at High Pressures. 9. Phase Separation and Critical Phenomena in 23 (n-Alkane + Water) Mixtures., J. Chem. Thermodyn., 1990, 22, 335. [all data]

Morita, Sato, et al., 1989
Morita, T.; Sato, H.; Uematsu, M.; Watanabe, K., PVT Properties and Vapor-Pressures of Ordinary Water Substance in the Critical Region, Physica A: (Amsterdam), 1989, 156, 436. [all data]

Aleksandrov, 1986
Aleksandrov, A.A., Critical Parameters of Ordinary and Heavy Water, Teploenergetika, 1986, No. 1, 74. [all data]

Sifner, 1985
Sifner, O., Recommended Values of Critical Parameters of Ordinary and Heavy Water, Chem. Listy, 1985, 79, 199. [all data]

Liu and Lindsay, 1970
Liu, C.-T.; Lindsay, W.T., Jr., Vapor Pressure of D₂O from 106 to 300 ºC, J. Chem. Eng. Data, 1970, 15, 4, 510-513, https://doi.org/10.1021/je60047a015 . [all data]

Bridgeman and Aldrich, 1964
Bridgeman, O.C.; Aldrich, E.W., Vapor Pressure Tables for Water, J. Heat Transfer, 1964, 86, 2, 279-286, https://doi.org/10.1115/1.3687121 . [all data]

Gubkov, Fermor, et al., 1964
Gubkov, A.N.; Fermor, N.A.; Smirnov, N.I., Vapor Pressure of Mono-Poly Systems, Zh. Prikl. Khim. (Leningrad), 1964, 37, 2204-2210. [all data]

Stull, 1947
Stull, Daniel R., Vapor Pressure of Pure Substances. Organic and Inorganic Compounds, Ind. Eng. Chem., 1947, 39, 4, 517-540, https://doi.org/10.1021/ie50448a022 . [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Snow and Thomas, 1990
Snow, K.B.; Thomas, T.F., Mass spectrum, ionization potential, and appearance potentials for fragment ions of sulfuric acid vapor, Int. J. Mass Spectrom. Ion Processes, 1990, 96, 49. [all data]

Page, Larkin, et al., 1988
Page, R.H.; Larkin, R.J.; Yhen, Y.R.; Lee, Y.T., High-resolution photoionization spectrum of water molecules in a supersonic beam, J. Chem. Phys., 1988, 88, 2249. [all data]

Reutt, Wang, et al., 1986
Reutt, J.E.; Wang, L.S.; Lee, Y.T.; Shirley, D.A., Molecular beam photoelectron spectroscopy and femtosecond intramolecular dynamics of H₂O⁺ and D₂O⁺, J. Chem. Phys., 1986, 85, 6928. [all data]

Grade, Wienecke, et al., 1983
Grade, M.; Wienecke, J.; Rosinger, W.; Hirschwald, W., Electron impact investigation of the molecules SeS(g) and TeSe(g) under high-temperature equilibrium conditions, Ber. Bunsen-Ges. Phys. Chem., 1983, 87, 355. [all data]

Lefaivre and Marmet, 1978
Lefaivre, D.; Marmet, P., Electroionization of D₂O and H₂O and study of fragments H⁺ and OH⁺, Can. J. Phys., 1978, 56, 1549. [all data]

Gurtler, Saile, et al., 1977
Gurtler, P.; Saile, V.; Koch, E.E., Rydberg series in the absorption spectra of H₂O and D₂O in the vacuum ultraviolet, Chem. Phys. Lett., 1977, 51, 386. [all data]

Botter and Carlier, 1977
Botter, R.; Carlier, J., Spectre de photoelectrons et calcul des facteurs de Franck-Condon pour H₂O, D₂O, HDO, J. Electron Spectrosc. Relat. Phenom., 1977, 12, 55. [all data]

Kronebusch and Berkowitz, 1976
Kronebusch, P.L.; Berkowitz, J., Photodissociative ionization in the 21-41 eV region: O₂, N₂, CO, NO, CO₂, H₂O, NH₃ and CH₄, Int. J. Mass Spectrom. Ion Phys., 1976, 22, 283. [all data]

Dixon, Duxbury, et al., 1976
Dixon, R.N.; Duxbury, G.; Rabalais, J.W.; Asbrink, L., Rovibronic structure in the photoelectron spectra of H₂O, D₂O and HDO, Mol. Phys., 1976, 31, 423. [all data]

Karlsson, Mattson, et al., 1975
Karlsson, L.; Mattson, L.; Jadrny, R.; Albridge, R.G.; Pinchas, S.; Bergmark, T.; Siegbahn, K., Isotopic and vibronic coupling effects in the valence electron spectra of H₂¹⁶O, H₂¹⁸O, and D₂¹⁶O, J. Chem. Phys., 1975, 62, 4745. [all data]

Debies and Rabalais, 1975
Debies, T.P.; Rabalais, J.W., Calculated photoionization cross-sections and angular distributions for the isoelectronic series Ne, HF, H₂O, NH₃, and CH₄, J. Am. Chem. Soc., 1975, 97, 487. [all data]

Rabalais, Debies, et al., 1974
Rabalais, J.W.; Debies, T.P.; Berkosky, J.L.; Huang, J.-T.J.; Ellison, F.O., Calculated photoionization cross sections relative experimental photoionization intensities for a selection of small molecules, J. Chem. Phys., 1974, 61, 516. [all data]

Bergmark, Karlsson, et al., 1974
Bergmark, T.; Karlsson, L.; Jadrny, R.; Mattsson, L.; Albridge, R.G.; Siegbahn, K., Isotopic effects in the electron spectra of H₂¹⁶O, H₂¹⁸O, and D₂¹⁶O, J. Electron Spectrosc. Relat. Phenom., 1974, 4, 85. [all data]

Robin and Kuebler, 1973
Robin, M.B.; Kuebler, N.A., Excited electronic states of the simple alcohols, J. Electron Spectrosc. Relat. Phenom., 1973, 1, 13. [all data]

Morrison and Traeger, 1973
Morrison, J.D.; Traeger, J.C., Ionization and dissociation by electron impact. I. H₂O and H₂S, Int. J. Mass Spectrom. Ion Phys., 1973, 11, 77. [all data]

Katayama, Huffman, et al., 1973
Katayama, D.H.; Huffman, R.E.; O'Bryan, C.L., Absorption and photoionization cross sections for H₂O and D₂O in the vacuum ultraviolet, J. Chem. Phys., 1973, 59, 4309. [all data]

Potts and Price, 1972
Potts, A.W.; Price, W.C., Photoelectron spectra and valence shell orbital structures of groups V VI hydrides, Proc. R. Soc. London A:, 1972, 326, 181. [all data]

Asbrink and Rabalais, 1971
Asbrink, L.; Rabalais, J.W., Comments on the high resolution photoelectron spectrum of H₂O and D₂O, Chem. Phys. Lett., 1971, 12, 182. [all data]

Cermak, 1968
Cermak, V., Penning ionization electron spectroscopy. I. Determination of ionization potentials of polyatomic molecules, Collection Czech. Chem. Commun., 1968, 33, 2739. [all data]

Brundle and Turner, 1968
Brundle, C.R.; Turner, D.W., High resolution molecular photoelectron spectroscopy. II.Water and deuterium oxide, Proc. Roy. Soc. (London), 1968, A307, 27. [all data]

Dibeler, Walker, et al., 1966
Dibeler, V.H.; Walker, J.A.; Rosenstock, H.M., Mass spectrometric study of photoionization. V.Water and ammonia, J.Res. NBS, 1966, 70A, 459. [all data]

Brehm, 1966
Brehm, B., Massenspektrometrische Untersuchung der Photoionisation von Molekulen, Z. Naturforsch., 1966, 21a, 196. [all data]

Nicholson, 1965
Nicholson, A.J.C., Photoionization-efficiency curves. II. False and genuine structure, J. Chem. Phys., 1965, 43, 1171. [all data]

Frost and McDowell, 1958
Frost, D.C.; McDowell, C.A., Excited states of the molecular ions of hydrogen fluoride, hydrogen iodide, water, hydrogen sulphide, and ammonia, Can. J. Chem., 1958, 36, 39. [all data]

Price, 1936
Price, W.C., The far ultraviolet absorption spectra and ionization potentials of H₂O and H₂S, J. Chem. Phys., 1936, 4, 147. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Campbell, Liesegang, et al., 1979
Campbell, M.J.; Liesegang, J.; Riley, J.D.; Leckey, R.C.G.; Jenkin, J.G.; Poole, R.T., The electronic structure of the valence bands of solid NH₃ and H₂O studied by ultraviolet photoelectron spectroscopy, J. Electron Spectrosc. Relat. Phenom., 1979, 15, 83. [all data]

Benoit and Harrison, 1977
Benoit, F.M.; Harrison, A.G., Predictive value of proton affinity. Ionization energy correlations involving oxygenated molecules, J. Am. Chem. Soc., 1977, 99, 3980. [all data]

Wieczorek, Koenig, et al., 1975
Wieczorek, J.S.; Koenig, T.; Balle, T., The He(I) photoelectron spectra of amine n-oxides, J. Electron Spectrosc. Relat. Phenom., 1975, 6, 215. [all data]

Banna and Shirley, 1975
Banna, M.S.; Shirley, D.A., Molecular photoelectron spectroscopy at 132.3 eV. The second-row hydrides, J. Chem. Phys., 1975, 63, 4759. [all data]

Schweig and Thiel, 1974
Schweig, A.; Thiel, W., Photoionization cross sections: He I- and He II-photoelectron spectra of homologous oxygen and sulphur compounds, Mol. Phys., 1974, 27, 265. [all data]

Appell and Durup, 1973
Appell, J.; Durup, J., The formation of protons by impact of low energy electrons on water molecules, Int. J. Mass Spectrom. Ion Phys., 1973, 10, 247. [all data]

Cottin, 1959
Cottin, M., Etude des ions produits par impact electronique dans la vapeur d'eau, J. Chim. Phys., 1959, 56, 1024. [all data]

McCulloh, 1976
McCulloh, K.E., Energetics and mechanisms of fragment ion formation in the photoionization of normal and deuterated water and ammonia, Int. J. Mass Spectrom. Ion Phys., 1976, 21, 333. [all data]

Foner and Hudson, 1956
Foner, S.N.; Hudson, R.L., Ionization potential of the OH free radical by mass spectrometry, J. Chem. Phys., 1956, 25, 602. [all data]

Ehrhardt and Kresling, 1967
Ehrhardt, H.; Kresling, A., Die dissoziative Ionisation von N₂, O₂, H₂O, CO₂ und Athan, Z. Naturforsch., 1967, 22a, 2036. [all data]

Smith, Kim, et al., 1997
Smith, J.R.; Kim, J.B.; Lineberger, W.C., High-resolution Threshold Photodetachment Spectroscopy of OH-, Phys. Rev. A, 1997, 55, 3, 2036, https://doi.org/10.1103/PhysRevA.55.2036 . [all data]

Check, Faust, et al., 2001
Check, C.E.; Faust, T.O.; Bailey, J.M.; Wright, B.J.; Gilbert, T.M.; Sunderlin, L.S., Addition of Polarization and Diffuse Functions to the LANL2DZ Basis Set for P-Block Elements, J. Phys. Chem. A,, 2001, 105, 34, 8111, https://doi.org/10.1021/jp011945l . [all data]

Notes

Go To: Top, Condensed phase thermochemistry data, Phase change data, Gas phase ion energetics 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°liquid	Entropy of liquid at standard conditions
  S°liquid,1 bar	Entropy of liquid at standard conditions (1 bar)
  Tboil	Boiling point
  Tc	Critical temperature
  ΔfH°liquid	Enthalpy of formation of liquid at standard conditions
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ρc	Critical density

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
• The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.
• Customer support for NIST Standard Reference Data products.