Sodium superoxide

Sodium superoxide

Names
IUPAC name sodium(I) superoxide
Other names sodium superoxide
Identifiers
CAS Number	12034-12-7 Y
Jmol 3D model	Interactive image
PubChem	61542
RTECS number	WE2860010
InChI InChI=1S/Na.O2/c;1-2/q+1;
SMILES O=O.[Na+]
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
Specific heat capacity (C)	72.1 J/mol K
Std molar entropy (So298)	115.9 J/mol K
Std enthalpy of formation (ΔfHo298)	-260.2 kJ/mol
Gibbs free energy (ΔfG˚)	-218.4 kJ/mol
Vapor pressure	{{{value}}}
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

Sodium superoxide is the inorganic compound with 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.

Preparation

NaO₂ is prepared by treating sodium peroxide with oxygen at high pressures:

Na₂O₂ + O₂ → 2 NaO₂

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

Na(in NH₃) + O₂ → NaO₂

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. It crystallizes in the NaCl motif.