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Sodium superoxide

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Title: Sodium superoxide  
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Subject: Sodium oxide, Sodium zincate, Sodium bismuthate, Sodium hypophosphite, Sodium metaborate
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Sodium superoxide

Sodium superoxide
CAS number  YesY
RTECS number WE2860010
Jmol-3D images Image 1
Molecular 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
Crystal structure cubic
heat capacity
72.1 J/mol K
Std molar
115.9 J/mol K
Std enthalpy of
-260.2 kJ/mol
Gibbs free energy ΔG -218.4 kJ/mol
EU classification Corrosive
R-phrases R35
S-phrases S1/2, S26, S37/39, S45
NFPA 704
Flash point Non flammable
Related compounds
Other anions sodium oxide
sodium peroxide
Other cations potassium superoxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY   YesY/N?)

Sodium superoxide is the formula NaO2. 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:[1]

Na2O2 + O2 → 2 NaO2

It can also be prepared by careful oxygenation of a solution of sodium in ammonia:

Na(in NH3) + O2 → NaO2


The product is paramagnetic, as expected for a salt of the O
anion. It hydrolyses readily to give a mixture of sodium hydroxide, oxygen and hydrogen peroxide.[2] It crystallizes in the NaCl motif.


  1. ^ Stephen E. Stephanou, Edgar J. Seyb Jr., Jacob Kleinberg "Sodium Superoxide" Inorganic Syntheses 1953; Vol. 4, 82-85.
  2. ^ Sasol Encyclopaedia of Science and Technology , G.C. Gerrans, P. Hartmann-Petersen , p.243 "sodium oxides" , google books link
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