sodium oxide
{{chembox
| Watchedfields = changed
| verifiedrevid = 441025998
| ImageFile = Na2O.jpg
| ImageFileL1 = Sodium-oxide-unit-cell-3D-balls-B.png
| ImageSizeL1 = 100px
| ImageNameL1 = Sodium oxide
| ImageFileR1 = Sodium-oxide-3D-polyhedra.png
| ImageSizeR1 = 100px
| ImageNameR1 = Sodium oxide
| IUPACName = Sodium oxide
| OtherNames = {{ubl|Disodium oxide|Natrium oxide (historic)|Soda|Sodium oxidosodium}}
| Section1 = {{Chembox Identifiers
|CASNo = 1313-59-3
|CASNo_Ref = {{cascite|correct|CAS}}
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = 3075U8R23D
|PubChem = 73971
|UNNumber = 1825
|EINECS = 215-208-9
|InChI = 1S/2Na.O/q2*+1;-2
|SMILES = [O-2].[Na+].[Na+]
}}
| Section2 = {{Chembox Properties
|Na=2 | O=1
|Appearance = white solid
|Density = 2.49 g/cm3
|Solubility = Reacts to form NaOH
|SolubleOther = Reacts with ethanol
|MeltingPtC = 1132
|BoilingPtC = 1950
|SublimationConditions = sublimates at 1275 °C
|BoilingPt_notes = sublimates
|MagSus = −19.8·10−6 cm3/mol
}}
| Section3 = {{Chembox Structure
|CrystalStruct = Antifluorite (face centered cubic), cF12
|SpaceGroup = Fm3m, No. 225
|Coordination = Tetrahedral ({{chem2|Na+}}); cubic ({{chem2|O(2−)}})
}}
| Section4 = {{Chembox Thermochemistry
|DeltaHf = −416 kJ/mol{{cite book|author = Zumdahl, Steven S.|title =Chemical Principles 6th Ed.|publisher = Houghton Mifflin Company|year = 2009|isbn = 978-0-618-94690-7|page = A23}}
|DeltaGf = −377.1 kJ/mol
|HeatCapacity = 72.95 J/(mol·K)
}}
| Section5 = {{Chembox Hazards
|ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1653.htm ICSC 1653]
|GHSPictograms = {{GHS05}}{{Sigma-Aldrich|id=208116|name=Sodium oxide|accessdate=2014-05-25}}
|HPhrases = {{H-phrases|314}}
|PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
|MainHazards = corrosive, reacts violently with water
|NFPA-H = 3
|NFPA-F = 0
|NFPA-R = 1
|NFPA-S = W
|FlashPt = nonflammable
}}
| Section6 = {{Chembox Related
|OtherAnions = {{ubl|Sodium sulfide|Sodium selenide|Sodium telluride|Sodium polonide}}
|OtherCations = {{ubl|Lithium oxide|Potassium oxide|Rubidium oxide|Caesium oxide}}
|OtherFunction = {{ubl|Sodium peroxide|Sodium superoxide|Sodium ozonide}}
|OtherFunction_label = sodium oxides
|OtherCompounds = Sodium hydroxide
}}
}}
Sodium oxide is a chemical compound with the formula {{chem2|Na2O}}. It is used in ceramics and glasses. It is a white solid but the compound is rarely encountered. Instead "sodium oxide" is used to describe components of various materials such as glasses and fertilizers which contain oxides that include sodium and other elements. Sodium oxide is a component.
Structure
The structure of sodium oxide has been determined by X-ray crystallography. Most alkali metal oxides {{chem2|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 calcium fluoride, with sodium ions tetrahedrally coordinated to 4 oxide ions and oxide cubically coordinated to 8 sodium ions.{{cite journal| title = Gitterstruktur der oxyde, sulfide, selenide und telluride des lithiums, natriums und kaliums | journal = Zeitschrift für Elektrochemie und Angewandte Physikalische Chemie | year = 1934 | volume = 40 | pages = 588–93| last1 = Zintl | first1 = E. | last2 = Harder | first2 = A. | author3 = Dauth B. | issue = 8 | author-link1 = Eduard Zintl | doi=10.1002/bbpc.19340400811 | s2cid = 94213844}}Wells, A. F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press {{ISBN|0-19-855370-6}}
Preparation
Sodium oxide is produced by the reaction of sodium with sodium hydroxide, sodium peroxide, or sodium nitrite:{{Greenwood&Earnshaw2nd|page=}}
:{{chem2|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.{{cite book|author=E. Dönges|chapter=Sodium Oxide (IV)|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1pages=975-6}}
A second method involves heating a mixture of sodium azide and sodium nitrate:
:{{chem2|5 NaN3 + NaNO3 → 3 Na2O + 8 N2}}
Burning sodium in air produces a mixture of {{chem2|Na2O}} and sodium peroxide ({{chem2|Na2O2}}).
A third much less known method involves heating sodium metal with iron(III) oxide (rust):
:{{chem2|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 {{chem2|Na2O}}. Furthermore, such glasses are not made from sodium oxide, but the equivalent of {{chem2|Na2O}} is added in the form of "soda" (sodium carbonate), which loses carbon dioxide at high temperatures:
:{{chem2|Na2CO3 → Na2O + CO2}}
:{{chem2|Na2O + SiO2 → Na2SiO3}}
:{{chem2|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 {{chem2|Na2[SiO2]_{x}[SiO3]}}-based material is somewhat more flexible.
Reactions
Sodium oxide reacts readily and irreversibly with water to give sodium hydroxide:
:{{chem2|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
{{reflist}}
{{Commons category|Sodium oxide}}
{{Sodium compounds}}
{{Oxides}}
{{oxygen compounds}}