 | |||
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| Names | |||
|---|---|---|---|
| IUPAC name Sodium oxide | |||
Other names
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| Identifiers | |||
3D model (JSmol) | |||
| ChemSpider | |||
| ECHA InfoCard | 100.013.827 | ||
| EC Number |
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| UNII | |||
| 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 formNaOH | |||
| Solubility | Reacts withethanol | ||
| −19.8·10−6 cm3/mol | |||
| Structure | |||
| Antifluorite (face centered cubic),cF12 | |||
| Fm3m, No. 225 | |||
| Tetrahedral (Na+); cubic (O2−) | |||
| Thermochemistry | |||
| 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⦵) | −377.1 kJ/mol | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | corrosive, reacts violently with water | ||
| GHS labelling: | |||
 [2] | |||
| H314 | |||
| P260,P264,P280,P301+P330+P331,P303+P361+P353,P304+P340,P305+P351+P338,P310,P321,P363,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | nonflammable | ||
| Safety data sheet (SDS) | ICSC 1653 | ||
| Related compounds | |||
Otheranions | |||
Othercations | |||
Related compounds | Sodium hydroxide | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Sodium oxide is achemical compound with the formulaNa2O. It is used inceramics andglasses. 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.
The structure of sodium oxide has been determined byX-ray crystallography. Mostalkali metal oxidesM2O (M =Li,Na,K,Rb) crystallise in theantifluorite structure. In this motif the positions of theanions andcations are reversed relative to their positions inCaF2, withsodium ions tetrahedrally coordinated to 4 oxide ions and oxide cubically coordinated to 8 sodium ions.[3][4]
Sodium oxide is produced by the reaction ofsodium withsodium hydroxide,sodium peroxide, orsodium nitrite:[5]
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 ofsodium azide andsodium nitrate:[6]
Burning sodium inair produces a mixture ofNa2O andsodium peroxide (Na2O2):
A third much less known method involves asingle displacement reaction when heating sodium metal withiron(III) oxide (rust):
the reaction should be done in an inert atmosphere to avoid the reaction of sodium with the air instead.
Glasses are often described in terms of their sodium oxide content although they do not really containNa2O. Furthermore, such glasses are not made from sodium oxide, but the equivalent ofNa2O is added in the form of "soda" (sodium carbonate), which losescarbon dioxide at high temperatures:
A typical manufacturedglass 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. Suchsoda-lime glass has a much lower melting temperature than pure silica and has slightly higher elasticity. These changes arise because theNa2[SiO2]x[SiO3]-based material is somewhat more flexible.
Sodium oxide reacts readily and irreversibly with water to givesodium hydroxide:
Because of this reaction, sodium oxide is sometimes referred to as thebase anhydride of sodium hydroxide (more archaically, "anhydride of caustic soda").
