Sodium oxide

Sodium oxide
IUPAC name Sodium oxide
Other names Disodium oxide
Identifiers
CAS number	1313-59-3 Y
PubChem	73971
UN number	1825
Properties
Molecular formula	Na2O
Molar mass	61.9789 g/mol
Appearance	White solid
Density	2.27 g/cm3
Melting point	1132°C
Boiling point	1950 °C decomposes
Solubility in water	reacts violently to form NaOH
Structure
Crystal structure	Antifluorite (face centered cubic), cF12
Space group	Fm3m, No. 225
Coordination geometry	Tetrahedral (Na+); cubic (O2–)
Thermochemistry
Std enthalpy of formation ΔfHo298	−414.2 kJ/mol
Standard molar entropy So298	75.1 J mol−1 K−1
Hazards
MSDS	ICSC 1653
EU Index	Not listed
Main hazards	Corrosive, reacts violently with water
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
Y oxide (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium oxide (SOX) is a chemical compound with the formula Na₂O. It is used in ceramics and glasses, though not in a raw form. Treatment with water affords sodium hydroxide.

Na₂O + H₂O → 2 NaOH

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.^[1][2]

Preparation

Sodium oxide is produced by the reaction of sodium with sodium hydroxide, sodium peroxide, or sodium nitrite:^[3]

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

Glass making

Sodium oxide is a significant component of glasses and windows although it is added in the form of "soda" (sodium carbonate). Sodium oxide does not explicitly exist in glasses, since glasses are complex cross-linked polymers. 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 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 react to form sodium silicates of the general formula Na₂[SiO₂]_x[SiO₃].

Na₂CO₃ → Na₂O + CO₂

Na₂O + SiO₂ → Na₂SiO₃

References

1. ^ 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 
2. ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
3. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.

External links

• Sodium oxide information at Webelements.
• External MSDS Data Sheet.