Sodium oxide

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Sodium oxide
Names
IUPAC name
Sodium oxide
Other names
Disodium monoxide
Disodium oxide
Properties
Na2O
Molar mass 61.98 g/mol
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)
Reacts
Solubility Reacts with alcohols, carboxylic acids, mineral acids
Insoluble in ethers, hydrocarbons
Vapor pressure ~0 mmHg
Thermochemistry
73 J·mol-1·K-1
-416 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point Nn-flammable
Related compounds
Related compounds
Sodium peroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium oxide is a chemical compound with the formula Na2O. It is one of the three oxides of sodium, the other being sodium peroxide and sodium superoxide.

Properties

Chemical

Sodium oxide reacts with water to give sodium hydroxide. The reaction is highly exothermic.

Na2O + H2O → 2 NaOH

Reaction with alcohols gives their corresponding alkoxides.

Physical

Sodium oxide is a white solid, which reacts with water and atmospheric moisture. It melts at 1,132 °C and boils at 1,950 °C, though it begins to sublime at 1275 °C.

Availability

Sodium oxide is sold by chemical suppliers, though it's difficult to get hold of.

Preparation

Sodium oxide can be prepared via several routes.

The most common method involves burning sodium in air. The reaction produces both sodium oxide and sodium peroxide, with the latter being around 20% of the product.

The reaction of metallic sodium with sodium hydroxide, sodium peroxide or sodium nitrite will also give sodium oxide.

Another common route involves the calcination of sodium carbonate at 800-1000 °C.

Na2CO3 → Na2O + CO2

This reaction requires constant high temperature and takes place over a long time period.

A lower temperature route involves the decomposition of sodium ascorbate, which can be easily obtained by reacting sodium bicarbonate with ascorbic acid. The decomposition begins at 218 °C, yielding sodium oxide and furanes.[1]

Decomposition of sodium nitrite will give off nitrogen oxides and leave behind sodium oxide. Decomposition begins at around 320 °C.

The last three reactions give hot sodium oxide which can rapidly absorb moisture and carbon dioxide and convert back to sodium hydroxide/carbonate. Cooling of the hot sodium hydroxide should be done in an inert medium.

Projects

  • Make pure sodium hydroxide
  • Dry CO2 scrubber
  • Make soda glass

Handling

Safety

Sodium oxide is extremely corrosive and reaction with water is highly exothermic.

Storage

Should be stored in air-tight containers. Schlenk flasks, gloveboxes, sealed ampoules are recommended.

Disposal

Sodium oxide should be neutralized by slow addition in cold acidified water. Aqueous phosphoric acid can be used as it has low volatility.

References

  1. Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 310

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