Selected ATcT [1, 2] enthalpy of formation based on version 1.172 of the Thermochemical Network [3]

This version of ATcT results[3] was generated by additional expansion of version 1.156 to include species relevant to a study of photodissociation of formamide[4].

Water dimer

Formula: (H2O)2 (g)

CAS RN: 25655-83-8

ATcT ID: 25655-83-8*0

SMILES: O.O

InChI: InChI=1S/2H2O/h2*1H2

InChIKey: JEGUKCSWCFPDGT-UHFFFAOYSA-N

Hills Formula: H4O2

2D Image:

Aliases: (H2O)2; Water dimer; Dihydrol

Relative Molecular Mass: 36.03056 ± 0.00066

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
-491.034	-499.074	± 0.044	kJ/mol

3D Image of (H2O)2 (g)

spin ON spin OFF

Top contributors to the provenance of Δ_fH° of (H2O)2 (g)

The 20 contributors listed below account only for 64.7% of the provenance of Δ_fH° of (H2O)2 (g).
A total of 325 contributors would be needed to account for 90% of the provenance.

Please note: The list is limited to 20 most important contributors or, if less, a number sufficient to account for 90% of the provenance. The Reference acts as a further link to the relevant references and notes for the measurement. The Measured Quantity is normaly given in the original units; in cases where we have reinterpreted the original measurement, the listed value may differ from that given by the authors. The quoted uncertainty is the a priori uncertainty used as input when constructing the initial Thermochemical Network, and corresponds either to the value proposed by the original authors or to our estimate; if an additional multiplier is given in parentheses immediately after the prior uncertainty, it corresponds to the factor by which the prior uncertainty needed to be multiplied during the ATcT analysis in order to make that particular measurement consistent with the prevailing knowledge contained in the Thermochemical Network.

Contribution (%)	TN ID	Reaction	Measured Quantity	Reference
29.4	125.2	1/2 O2 (g) + H2 (g) → H2O (cr,l)	Δ_rH°(298.15 K) = -285.8261 ± 0.040 kJ/mol	Rossini 1939, Rossini 1931, Rossini 1931b, note H2Oa, Rossini 1930
8.7	2373.7	CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (cr,l)	Δ_rH°(298.15 K) = -890.578 ± 0.078 kJ/mol	Schley 2010
7.9	2375.1	2 H2 (g) + C (graphite) → CH4 (g)	Δ_rG°(1165 K) = 37.521 ± 0.068 kJ/mol	Smith 1946, note COf, 3rd Law
2.0	115.11	H2O (g) → O (g) + 2 H (g)	Δ_rH°(0 K) = 917.80 ± 0.15 kJ/mol	Thorpe 2021
1.8	157.1	OH (g) → [OH]+ (g)	Δ_rH°(0 K) = 104989 ± 5 (×2.378) cm-1	Wiedmann 1992, note unc
1.5	167.6	H2O (g) → [OH]+ (g) + H (g)	Δ_rH°(0 K) = 18.1183 ± 0.0015 (×1.067) eV	Bodi 2014
1.4	152.1	OH (g) → O (g) + H (g)	Δ_rH°(0 K) = 35580 ± 15 cm-1	Sun 2020
1.3	1731.1	N2 (g) + 3 H2O (cr,l) + 2 H+ (aq) → 3/2 O2 (g) + 2 [NH4]+ (aq)	Δ_rH°(298.15 K) = 141.292 ± 0.119 kcal/mol	Vanderzee 1972c
1.2	169.1	[OH]- (g) → O- (g) + H (g)	Δ_rH°(0 K) = 4.7796 ± 0.0010 (×2) eV	Martin 2001, est unc
1.2	2373.4	CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (cr,l)	Δ_rH°(298.15 K) = -890.61 ± 0.21 kJ/mol	Dale 2002
1.1	2268.11	CO (g) → C (g) + O (g)	Δ_rH°(0 K) = 1071.92 ± 0.10 kJ/mol	Thorpe 2021
1.0	167.7	H2O (g) → [OH]+ (g) + H (g)	Δ_rH°(0 K) = 18.1190 ± 0.002 eV	Bodi 2014
0.8	167.5	H2O (g) → [OH]+ (g) + H (g)	Δ_rH°(0 K) = 18.1177 ± 0.0015 (×1.477) eV	Bodi 2014
0.7	2373.8	CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (cr,l)	Δ_rH°(298.15 K) = -890.482 ± 0.260 kJ/mol	Haloua 2015
0.7	2373.6	CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (cr,l)	Δ_rH°(298.15 K) = -890.44 ± 0.26 kJ/mol	GOMB Ref Calorimeter, Alexandrov 2002
0.7	175.1	[OH]+ (g) → O+ (g) + H (g)	Δ_rH°(0 K) = 40412.0 ± 2.2 cm-1	Moselhy 1975, note unc
0.7	2285.3	CO (g) + H2O (g) → CO2 (g) + H2 (g)	Δ_rG°(893 K) = -6.369 ± 0.283 kJ/mol	Meyer 1938, note COi, 3rd Law
0.5	1542.4	NNO (g) + CO (g) → CO2 (g) + N2 (g)	Δ_rH°(293.15 K) = -365.642 ± 0.243 kJ/mol	Fenning 1933, note N2Oa
0.5	2278.2	CO (g) → C+ (g) + O (g)	Δ_rH°(0 K) = 22.3713 ± 0.0015 eV	Ng 2007
0.5	225.4	HOOH (g) → 2 H (g) + 2 O (g)	Δ_rH°(0 K) = 1054.84 ± 0.56 kJ/mol	Harding 2008

Top 10 species with enthalpies of formation correlated to the Δ_fH° of (H2O)2 (g)

Please note: The correlation coefficients are obtained by renormalizing the off-diagonal elements of the covariance matrix by the corresponding variances.
The correlation coefficient is a number from -1 to 1, with 1 representing perfectly correlated species, -1 representing perfectly anti-correlated species, and 0 representing perfectly uncorrelated species.

Correlation Coefficent (%)	Species Name	Formula	Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units	Relative Molecular Mass	ATcT ID
99.7	Water	H2O (g)	-238.907	-241.810	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*0
99.7	Oxonium	[H3O]+ (aq)		-285.804	± 0.022	kJ/mol	19.02267 ± 0.00037	13968-08-6*800
99.7	Water	H2O (cr,l)	-286.276	-285.804	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*500
99.7	Water	H2O (cr, l, eq.press.)	-286.278	-285.806	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*499
99.7	Water	H2O (g, ortho)	-238.622	-241.810	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*1
99.7	Water	H2O (g, para)	-238.907	-241.810	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*2
99.7	Water	H2O (l)		-285.804	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*590
99.7	Water	H2O (l, eq.press.)		-285.806	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*589
99.6	Water	H2O (cr)	-286.276	-292.717	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*510
99.6	Water	H2O (cr, eq.press.)	-286.278	-292.719	± 0.022	kJ/mol	18.01528 ± 0.00033	7732-18-5*509

Most Influential reactions involving (H2O)2 (g)

Please note: The list, which is based on a hat (projection) matrix analysis, is limited to no more than 20 largest influences.

Influence Coefficient	TN ID	Reaction	Measured Quantity	Reference
0.701	210.3	(H2O)2 (g) → [H3O]+ (g) + OH (g)	Δ_rH°(0 K) = 11.7556 ± 0.0020 eV	Bodi 2014
0.593	211.9	(H2O)2 (g) → [(H2O)2]+ (g)	Δ_rH°(0 K) = 10.848 ± 0.040 eV	Ruscic W1RO
0.265	213.3	(H2O)3 (g) → (H2O)2 (g) + H2O (g)	Δ_rH°(0 K) = 2726 ± 30 cm-1	Wang 2011, Samanta 2014
0.168	211.8	(H2O)2 (g) → [(H2O)2]+ (g)	Δ_rH°(0 K) = 10.850 ± 0.075 eV	Ruscic CBS-n
0.140	2971.5	(CH3OH)2 (g) + 2 H2O (g) → (H2O)2 (g) + 2 CH3OH (g)	Δ_rH°(0 K) = 1.58 ± 0.85 kcal/mol	Ruscic W1RO
0.125	2971.1	(CH3OH)2 (g) + 2 H2O (g) → (H2O)2 (g) + 2 CH3OH (g)	Δ_rH°(0 K) = 1.22 ± 0.90 kcal/mol	Ruscic G3X
0.125	2971.4	(CH3OH)2 (g) + 2 H2O (g) → (H2O)2 (g) + 2 CH3OH (g)	Δ_rH°(0 K) = 1.56 ± 0.90 kcal/mol	Ruscic CBS-n
0.125	2971.2	(CH3OH)2 (g) + 2 H2O (g) → (H2O)2 (g) + 2 CH3OH (g)	Δ_rH°(0 K) = 1.24 ± 0.90 kcal/mol	Ruscic G4
0.101	2971.3	(CH3OH)2 (g) + 2 H2O (g) → (H2O)2 (g) + 2 CH3OH (g)	Δ_rH°(0 K) = 1.34 ± 1.0 kcal/mol	Ruscic CBS-n
0.096	211.7	(H2O)2 (g) → [(H2O)2]+ (g)	Δ_rH°(0 K) = 10.919 ± 0.099 eV	Ruscic CBS-n
0.096	211.6	(H2O)2 (g) → [(H2O)2]+ (g)	Δ_rH°(0 K) = 10.861 ± 0.099 eV	Ruscic G3
0.095	215.1	(H2O)3 (g) + H2O (g) → 2 (H2O)2 (g)	Δ_rH°(0 K) = 1597 ± 50 cm-1	Wang 2011
0.039	208.1	2 H2O (l, eq.press.) → (H2O)2 (g)	Δ_rG°(270 K) = 29.1743 ± 0.0145 kJ/mol	Wagner 2002
0.039	205.1	(H2O)2 (g) → 2 H2O (g)	Δ_rG°(270 K) = -5.2441 ± 0.0145 kJ/mol	Wagner 2002
0.038	207.1	2 H2O (l, eq.press.) → (H2O)2 (g)	Δ_rG°(273.16 K) = 28.6437 ± 0.0147 kJ/mol	Wagner 2002
0.038	204.1	(H2O)2 (g) → 2 H2O (g)	Δ_rG°(273.16 K) = -5.4899 ± 0.0147 kJ/mol	Wagner 2002
0.036	208.2	2 H2O (l, eq.press.) → (H2O)2 (g)	Δ_rG°(280 K) = 27.5049 ± 0.0150 kJ/mol	Wagner 2002
0.036	205.2	(H2O)2 (g) → 2 H2O (g)	Δ_rG°(280 K) = -6.0210 ± 0.0150 kJ/mol	Wagner 2002
0.034	208.3	2 H2O (l, eq.press.) → (H2O)2 (g)	Δ_rG°(290 K) = 25.8628 ± 0.0155 kJ/mol	Wagner 2002
0.033	205.3	(H2O)2 (g) → 2 H2O (g)	Δ_rG°(290 K) = -6.7950 ± 0.0156 kJ/mol	Wagner 2002

References

1		B. Ruscic, R. E. Pinzon, M. L. Morton, G. von Laszewski, S. Bittner, S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner, Introduction to Active Thermochemical Tables: Several "Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 108, 9979-9997 (2004) [DOI: 10.1021/jp047912y]
2		B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, and A. F. Wagner, Active Thermochemical Tables: Thermochemistry for the 21^st Century. J. Phys. Conf. Ser. 16, 561-570 (2005) [DOI: 10.1088/1742-6596/16/1/078]
3		B. Ruscic and D. H. Bross, Active Thermochemical Tables (ATcT) values based on ver. 1.172 of the Thermochemical Network (2024); available at ATcT.anl.gov
4		K. L. Caster, N. A. Seifert, B. Ruscic, A. W. Jasper, and K. Prozument, Dynamics of HCN, NHC, and HNCO Formation in the 193 nm Photodissociation of Formamide J. Phys. Chem. A (in press) (2024) [DOI: 10.1021/acs.jpca.4c02232]
5		B. Ruscic, Uncertainty Quantification in Thermochemistry, Benchmarking Electronic Structure Computations, and Active Thermochemical Tables. Int. J. Quantum Chem. 114, 1097-1101 (2014) [DOI: 10.1002/qua.24605]
6		B. Ruscic and D. H. Bross, Thermochemistry Computer Aided Chem. Eng. 45, 3-114 (2019) [DOI: 10.1016/B978-0-444-64087-1.00001-2]

Formula

The aggregate state is given in parentheses following the formula, such as: g - gas-phase, cr - crystal, l - liquid, etc.

Uncertainties

The listed uncertainties correspond to estimated 95% confidence limits, as customary in thermochemistry (see, for example, Ruscic [5] and Ruscic and Bross[6]).
Note that an uncertainty of ± 0.000 kJ/mol indicates that the estimated uncertainty is < ± 0.000₅ kJ/mol.

Website Functionality Credits

The reorganization of the website was developed and implemented by David H. Bross (ANL).
The find function is based on the complete Species Dictionary entries for the appropriate version of the ATcT TN.
The molecule images are rendered by Indigo-depict.
The XYZ renderings are based on Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/.

Acknowledgement

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Contract No. DE-AC02-06CH11357.