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| Names | |||
|---|---|---|---|
| Preferred IUPAC name
Water | |||
| Systematic IUPAC name
Oxidane (not in common use)[3] | |||
Other names
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| Identifiers | |||
3D model (JSmol)
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| 3587155 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| DrugBank | |||
| EC Number |
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| 117 | |||
| KEGG | |||
PubChem CID
|
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| RTECS number |
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| UNII | |||
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| Properties | |||
| H 2O | |||
| Molar mass | 18.01528(33) g/mol | ||
| Appearance | Almost colorless or white crystalline solid, almost colorless liquid, with a hint of blue, colorless gas[4] | ||
| Odor | Odorless | ||
| Density | |||
| Melting point | 0.00 °C (32.00 °F; 273.15 K) [b] | ||
| Boiling point | 99.98 °C (211.96 °F; 373.13 K)[17][b] | ||
| Solubility | Poorly soluble in haloalkanes, aliphatic and aromatic hydrocarbons, ethers.[8] Improved solubility in carboxylates, alcohols, ketones, amines. Miscible with methanol, ethanol, propanol, isopropanol, acetone, glycerol, 1,4-dioxane, tetrahydrofuran, sulfolane, acetaldehyde, dimethylformamide, dimethoxyethane, dimethyl sulfoxide, acetonitrile. Partially miscible with diethyl ether, methyl ethyl ketone, dichloromethane, ethyl acetate, bromine. | ||
| Vapor pressure | 3.1690 kilopascals or 0.031276 atm at 25 °C[9] | ||
| Acidity (pKa) | 13.995[10][11][a] | ||
| Basicity (pKb) | 13.995 | ||
| Conjugate acid | Hydronium H3O+ (pKa = 0) | ||
| Conjugate base | Hydroxide OH– (pKb = 0) | ||
| Thermal conductivity | 0.6065 W/(m·K)[14] | ||
Refractive index (nD)
|
1.3330 (20 °C)[15] | ||
| Viscosity | 0.890 mPa·s (0.890 cP)[16] | ||
| Structure | |||
| Hexagonal | |||
| C2v | |||
| Bent | |||
| 1.8546 D[18] | |||
| Thermochemistry | |||
Heat capacity (C)
|
75.385 ± 0.05 J/(mol·K)[17] | ||
Std molar
entropy (S⦵298) |
69.95 ± 0.03 J/(mol·K)[17] | ||
Std enthalpy of
formation (ΔfH⦵298) |
−285.83 ± 0.04 kJ/mol[8][17] | ||
Gibbs free energy (ΔfG⦵)
|
−237.24 kJ/mol[8] | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards
|
Drowning Avalanche (as snow) Water intoxication | ||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Safety data sheet (SDS) | SDS | ||
| Related compounds | |||
Other anions
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Related solvents
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| Supplementary data page | |||
| Water (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |||
Water (H2O) is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound[20] and is described as the "universal solvent"[21] and the "solvent of life".[22] It is the most abundant substance on the surface of Earth[23] and the only common substance to exist as a solid, liquid, and gas on Earth's surface.[24] It is also the third most abundant molecule in the universe (behind molecular hydrogen and carbon monoxide).[23]
Water molecules form hydrogen bonds with each other and are strongly polar. This polarity allows it to dissociate ions in salts and bond to other polar substances such as alcohols and acids, thus dissolving them. Its hydrogen bonding causes its many unique properties, such as having a solid form less dense than its liquid form, a relatively high boiling point of 100 °C for its molar mass, and a high heat capacity.
Water is amphoteric, meaning that it can exhibit properties of an acid or a base, depending on the pH of the solution that it is in; it readily produces both H+
and OH−
ions.[c] Related to its amphoteric character, it undergoes self-ionization. The product of the activities, or approximately, the concentrations of H+
and OH−
is a constant, so their respective concentrations are inversely proportional to each other.[25]
- ^ "naming molecular compounds". www.iun.edu. Archived from the original on 24 September 2018. Retrieved 1 October 2018.
Sometimes these compounds have generic or common names (e.g., H2O is "water") and they also have systematic names (e.g., H2O, dihydrogen monoxide).
- ^ "Definition of Hydrol". Merriam-Webster. Archived from the original on 13 August 2017. Retrieved 21 April 2019.
- ^ Leigh, Favre & Metanomski 1998, p. 99.
- ^ Cite error: The named reference
Braun_1993_612was invoked but never defined (see the help page). - ^ a b c Tanaka, M; Girard, G; Davis, R; Peuto, A; Bignell, N (August 2001). "Recommended table for the density of water between 0 C and 40 C based on recent experimental reports". Metrologia. 38 (4): 301–309. doi:10.1088/0026-1394/38/4/3.
- ^ Lemmon, Eric W.; Bell, Ian H.; Huber, Marcia L.; McLinden, Mark O. "Thermophysical Properties of Fluid Systems". In Linstrom, P.J.; Mallard, W.G. (eds.). NIST Chemistry WebBook, NIST Standard Reference Database Number 69. National Institute of Standards and Technology. doi:10.18434/T4D303. Archived from the original on 23 October 2023. Retrieved 17 October 2023.
- ^ Lide 2003, Properties of Ice and Supercooled Water in Section 6.
- ^ a b c Anatolievich, Kiper Ruslan. "Properties of substance: water". Archived from the original on 2014-06-02. Retrieved 2014-06-01.
- ^ Lide 2003, Vapor Pressure of Water From 0 to 370 °C in Sec. 6.
- ^ Lide 2003, Chapter 8: Dissociation Constants of Inorganic Acids and Bases.
- ^ Weingärtner et al. 2016, p. 13.
- ^ "What is the pKa of Water". University of California, Davis. 2015-08-09. Archived from the original on 2016-02-14. Retrieved 2016-04-09.
- ^ Silverstein, Todd P.; Heller, Stephen T. (17 April 2017). "pKa Values in the Undergraduate Curriculum: What Is the Real pKa of Water?". Journal of Chemical Education. 94 (6): 690–695. Bibcode:2017JChEd..94..690S. doi:10.1021/acs.jchemed.6b00623.
- ^ Ramires, Maria L. V.; Castro, Carlos A. Nieto de; Nagasaka, Yuchi; Nagashima, Akira; Assael, Marc J.; Wakeham, William A. (1995-05-01). "Standard Reference Data for the Thermal Conductivity of Water". Journal of Physical and Chemical Reference Data. 24 (3): 1377–1381. Bibcode:1995JPCRD..24.1377R. doi:10.1063/1.555963. ISSN 0047-2689.
- ^ Lide 2003, 8—Concentrative Properties of Aqueous Solutions: Density, Refractive Index, Freezing Point Depression, and Viscosity.
- ^ Lide 2003, 6.186.
- ^ a b c d Water in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD)
- ^ Lide 2003, 9—Dipole Moments.
- ^ GHS: PubChem 962 Archived 2023-07-28 at the Wayback Machine
- ^ Greenwood & Earnshaw 1997, p. 620.
- ^ "Water, the Universal Solvent". U.S. Department of the Interior. usgs.gov (website). United States of America: USGS. October 22, 2019. Archived from the original on December 1, 2021. Retrieved December 15, 2020.
- ^ Reece et al. 2013, p. 48.
- ^ a b Weingärtner et al. 2016, p. 2.
- ^ Reece et al. 2013, p. 44.
- ^ "Autoprotolysis constant". IUPAC Compendium of Chemical Terminology. IUPAC. 2009. doi:10.1351/goldbook.A00532. ISBN 978-0-9678550-9-7. Archived from the original on 2019-04-29. Retrieved 2018-08-09.
Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).