Sodium oxide
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| Names | |||
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| IUPAC name
Sodium oxide
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| Other names
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| Identifiers | |||
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3D model (JSmol)
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PubChem CID
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| UN number | 1825 | ||
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| Properties | |||
| Na2O | |||
| Molar mass | 61.979 g·mol−1 | ||
| Appearance | white solid | ||
| Density | 2.49 g/cm3 | ||
| Melting point | 1,132 °C (2,070 °F; 1,405 K) | ||
| Boiling point | 1,950 °C (3,540 °F; 2,220 K) sublimates | ||
| sublimates at 1275 °C | |||
| Reacts to form NaOH | |||
| Solubility | Reacts with ethanol | ||
| −19.8·10−6 cm3/mol | |||
| Structure | |||
| Antifluorite (face centered cubic), cF12 | |||
| Fm3m, No. 225 | |||
| Tetrahedral (Page Module:Chem2/styles.css has no content.Na+); cubic (Page Module:Chem2/styles.css has no content.O2−) | |||
| Thermochemistry | |||
Heat capacity (C)
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72.95 J/(mol·K) | ||
Std molar
entropy (S⦵298) |
73 J/(mol·K)[1] | ||
Std enthalpy of
formation (ΔfH⦵298) |
−416 kJ/mol[1] | ||
Gibbs free energy (ΔfG⦵)
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−377.1 kJ/mol | ||
| Hazards | |||
| NFPA 704 (fire diamond) | Page Template:NFPA 704 diamond/styles.css has no content. | ||
| Flash point | nonflammable | ||
| Safety data sheet (SDS) | ICSC 1653 | ||
| Related compounds | |||
Other anions
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Other cations
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Related compounds
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Sodium hydroxide | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Template:Chembox Footer/trackingTemplate:Short description
Sodium oxide is a chemical compound with the formula Page Module:Chem2/styles.css has no content.Na2O. It is used in ceramics and glasses. It is a white solid. However, the compound itself is rarely encountered and instead, the name "sodium oxide" is used to describe components of various materials such as glasses and fertilizers which contain oxides that include sodium and other elements.
Structure
The structure of sodium oxide has been determined by X-ray crystallography. Most alkali metal oxides Page Module:Chem2/styles.css has no content.M2O (M = Li, Na, K, Rb) crystallise in the antifluorite structure. In this motif the positions of the anions and cations are reversed relative to their positions in Page Module:Chem2/styles.css has no content.CaF2, with sodium ions tetrahedrally coordinated to 4 oxide ions and oxide cubically coordinated to 8 sodium ions.[3][4]
Preparation
Sodium oxide is produced by the reaction of sodium with sodium hydroxide, sodium peroxide, or sodium nitrite:[5]
- Page Module:Chem2/styles.css has no content.2 NaOH + 2 Na → 2 Na2O + H2
To the extent that NaOH is contaminated with water, correspondingly greater amounts of sodium are employed. Excess sodium is distilled from the crude product.[6]
A second method involves heating a mixture of sodium azide and sodium nitrate:[6]
- Page Module:Chem2/styles.css has no content.5 NaN3 + NaNO3 → 3 Na2O + 8 N2
Burning sodium in air produces a mixture of Page Module:Chem2/styles.css has no content.Na2O and sodium peroxide (Page Module:Chem2/styles.css has no content.Na2O2):
- Page Module:Chem2/styles.css has no content.4 Na + O2 → 2Na2O
- and
- Page Module:Chem2/styles.css has no content.2 Na + O2 → Na2O2
A third much less known method involves a single displacement reaction when heating sodium metal with iron(III) oxide (rust):
- Page Module:Chem2/styles.css has no content.6 Na + Fe2O3 → 3 Na2O + 2 Fe
the reaction should be done in an inert atmosphere to avoid the reaction of sodium with the air instead.
Applications
Glassmaking
Glasses are often described in terms of their sodium oxide content although they do not really contain Page Module:Chem2/styles.css has no content.Na2O. Furthermore, such glasses are not made from sodium oxide, but the equivalent of Page Module:Chem2/styles.css has no content.Na2O is added in the form of "soda" (sodium carbonate), which loses carbon dioxide at high temperatures:
- Page Module:Chem2/styles.css has no content.Na2CO3 → Na2O + CO2
- Page Module:Chem2/styles.css has no content.Na2O + SiO2 → Na2SiO3
- Page Module:Chem2/styles.css has no content.Na2CO3 + SiO2 → Na2SiO3 + CO2
A typical manufactured glass contains around 15% sodium oxide, 70% silica (silicon dioxide), and 9% lime (calcium oxide). The sodium carbonate "soda" serves as a flux to lower the temperature at which the silica mixture melts. Such soda-lime glass has a much lower melting temperature than pure silica and has slightly higher elasticity. These changes arise because the Page Module:Chem2/styles.css has no content.Na2[SiO2]x[SiO3]-based material is somewhat more flexible.
Reactions
Sodium oxide reacts readily and irreversibly with water to give sodium hydroxide:
- Page Module:Chem2/styles.css has no content.Na2O + H2O → 2 NaOH
Because of this reaction, sodium oxide is sometimes referred to as the base anhydride of sodium hydroxide (more archaically, "anhydride of caustic soda").
References
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- ^ a b Page Module:Citation/CS1/styles.css has no content.Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 978-0-618-94690-7.
- ^ Sigma-Aldrich Co., Sodium oxide. Retrieved on 2014-05-25.
- ^ Page Module:Citation/CS1/styles.css has no content.Zintl, E.; Harder, A.; Dauth B. (1934). "Gitterstruktur der oxyde, sulfide, selenide und telluride des lithiums, natriums und kaliums". Zeitschrift für Elektrochemie und Angewandte Physikalische Chemie. 40 (8): 588–93. doi:10.1002/bbpc.19340400811. S2CID 94213844.
- ^ Wells, A. F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press Template:ISBN
- ^ Page Module:Citation/CS1/styles.css has no content.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
- ^ a b Page Module:Citation/CS1/styles.css has no content.E. Dönges (1963). "Sodium Oxide (IV)". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1pages=975-6. NY, NY: Academic Press.
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