Sodium oxide

Sodium oxide is a chemical compound with the formula Na2O. It is used in ceramics and glasses. The compound is the base anhydride of sodium hydroxide; when water is added to sodium oxide, NaOH is produced.

Na2O + H2O → 2 NaOH
Sodium oxide
Sodium oxide
Sodium oxide
Names
IUPAC name
Sodium oxide
Other names
Disodium oxide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.013.827
EC Number
  • 215-208-9
UNII
UN number 1825
Properties
Na2O
Molar mass 61.979 g·mol−1
Appearance white solid
Density 2.27 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 violently to form NaOH
Solubility reacts with ethanol
−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)
73 J/(mol·K)[1]
Std enthalpy of
formation (ΔfH⦵298)
 −416 kJ/mol[1]
−377.1 kJ/mol
Hazards
Main hazards corrosive, reacts violently with water
Safety data sheet ICSC 1653
GHS pictograms [2]
GHS hazard statements
 H314[2]
P280[2]
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
0
3
1
Flash point non-flammable
Related compounds
Other anions
 Sodium sulfide
Sodium selenide
Sodium telluride
Other cations
 Lithium oxide
Potassium oxide
Rubidium oxide
Caesium oxide
Related sodium oxides
 Sodium peroxide
Sodium superoxide
Related compounds
 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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Infobox references

The alkali metal oxides 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 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]

2 NaOH + 2 Na → 2 Na2O + H2
Na2O2 + 2 Na → 2 Na2O
2 NaNO2 + 6 Na → 4 Na2O + N2

Most of these reactions rely on the reduction of something by sodium, whether it is hydroxide, peroxide, or nitrite.

Burning sodium in air will produce Na2O and about 20% sodium peroxide Na2O2.

6 Na + 2 O2 → 2 Na2O + Na2O2

Applications

Glassmaking

Sodium oxide is a significant component of most glass, although it is added in the form of "soda" (sodium carbonate). Typically, 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. Soda glass has a much lower melting temperature than pure silica, and has slightly higher elasticity. These changes arise because the silicon dioxide and soda have reacted to form sodium silicates of the general formula Na2[SiO2]x[SiO3].

Na2CO3 → Na2O + CO2
Na2O + SiO2 → Na2SiO3

References
  1. Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X.
  2. Sigma-Aldrich Co., Sodium oxide. Retrieved on 2014-05-25.
  3. Zintl, E.; Harder, A.; Dauth B. (1934). "Gitterstruktur der oxyde, sulfide, selenide und telluride des lithiums, natriums und kaliums". Z. Elektrochem. Angew. Phys. Chem. 40: 588–93. doi:10.1002/bbpc.19340400811.
  4. Wells, A. F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
  5. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
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