Sodium superoxide
Sodium superoxide is the inorganic compound with the formula NaO2.[1] This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen.
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| Names | |
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| IUPAC name
sodium(I) superoxide | |
| Other names
sodium superoxide | |
| Identifiers | |
CAS Number |
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PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
Chemical formula |
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 |
Solubility in water |
Decomposes |
| Basicity (pKb) | N/A |
| Structure | |
Crystal structure |
cubic |
| Thermochemistry | |
Heat capacity (C) |
72.1 J/mol K |
Std molar entropy (S |
115.9 J/mol K |
Std enthalpy of formation (ΔfH⦵298) |
-260.2 kJ/mol |
Gibbs free energy (ΔfG˚) |
-218.4 kJ/mol |
| Hazards | |
EU classification (DSD) (outdated) |
Corrosive |
| R-phrases (outdated) | R35 |
| S-phrases (outdated) | S1/2, S26, S37/39, S45 |
| NFPA 704 (fire diamond) | 
0
3
1 OX |
| Flash point | Non flammable |
| Related compounds | |
Other anions |
sodium oxide sodium peroxide |
Other cations |
potassium superoxide |
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 | |
Preparation
NaO2 is prepared by treating sodium peroxide with oxygen at high pressures:[2]
- Na2O2 + O2 → 2 NaO2
It can also be prepared by careful oxygenation of a solution of sodium in ammonia:
- Na(in NH3) + O2 → NaO2
It is also produced, along with sodium peroxide, when sodium is stored under inappropriate conditions (e.g. in dirty or partially halogenated solvents).
Properties
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.[3] It crystallizes in the NaCl motif.
References
- Hayyan M., Hashim M.A., AlNashef I.M., Superoxide Ion: Generation and Chemical Implications, Chem. Rev., 2016, 116 (5), pp 3029–3085. DOI: 10.1021/acs.chemrev.5b00407
- Stephen E. Stephanou, Edgar J. Seyb Jr., Jacob Kleinberg "Sodium Superoxide" Inorganic Syntheses 1953; Vol. 4, 82-85.
- Sasol Encyclopaedia of Science and Technology , G.C. Gerrans, P. Hartmann-Petersen , p.243 "sodium oxides" , google books link
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