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Names | |
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IUPAC name sodium superoxide | |
Other names sodium superoxide sodium dioxide | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
PubChem CID | |
RTECS number |
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UNII | |
UN number | 2547 |
CompTox Dashboard (EPA) | |
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Properties | |
NaO2 | |
Molar mass | 54.9886 g/mol |
Appearance | Yellow to orange crystalline solid |
Density | 2.2 g/cm3 |
Melting point | 551.7 °C (1,025.1 °F; 824.9 K) |
Boiling point | Decomposes |
Decomposes | |
Basicity (pKb) | N/A |
Structure | |
cubic | |
Thermochemistry | |
Heat capacity (C) | 72.1 J/mol K |
Std molar entropy (S⦵298) | 115.9 J/mol K |
Std enthalpy of formation (ΔfH⦵298) | −260.2 kJ/mol |
Gibbs free energy (ΔfG⦵) | −218.4 kJ/mol |
Hazards | |
GHS labelling: | |
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Danger | |
H271, H314 | |
P210, P220, P260, P280, P303+P361+P353, P305+P351+P338 | |
NFPA 704 (fire diamond) | |
Flash point | Non flammable |
Related compounds | |
Other anions | sodium oxide sodium peroxide |
Other cations | Lithium superoxide Potassium superoxide Rubidium superoxide Caesium superoxide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Sodium superoxide is the inorganic compound with the formula Na O2. [1] This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen.
NaO2 is prepared by treating sodium peroxide with oxygen at high pressures: [2]
It can also be prepared by careful oxygenation of a solution of sodium in cryogenic liquid ammonia:
Although the existence of a sodium oxide higher than peroxide was speculated since 19th century, it was not until 1948 when American chemists were able to definitely synthesize it by the latter method. [3]
It is also produced, along with sodium peroxide, when sodium is stored under inappropriate conditions (e.g. in dirty or partially halogenated solvents)[ citation needed ].
The product is paramagnetic, as expected for a salt of the O−
2 anion. It hydrolyses readily to give a mixture of sodium hydroxide, oxygen and hydrogen peroxide. [4] It crystallizes in the NaCl motif.