Potassium superoxide

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Potassium superoxide
Unit cell of potassium superoxide
CAS number 12030-88-5 YesY
PubChem 61541
EC number 234-746-5
RTECS number TT6053000
Jmol-3D images Image 1
Molecular formula KO2
Molar mass 71.10 g mol−1
Appearance yellow solid
Density 2.14 g/cm3, solid
Melting point 560 °C (1,040 °F; 833 K) (decomposes)
Solubility in water decomposes
Crystal structure Body-centered cubic (O2)
Std molar
117 J·mol−1·K−1[1]
Std enthalpy of
−283 kJ·mol−1[1]
R-phrases 8-14-34
S-phrases 17-27-36/37/39
Main hazards corrosive, oxidant
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g., fluorine Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Other anions Potassium oxide
Potassium peroxide
Other cations Sodium superoxide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Potassium superoxide is the inorganic compound with the formula KO2. It is a yellow solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide ion. Potassium superoxide is used as an oxidizing agent in industrial chemistry, as a CO2 scrubber, H2O dehumidifier and O2 generator in rebreathers, spacecraft, submarines and spacesuit life support systems.

Production and reactions[edit]

Potassium superoxide is produced by burning molten potassium in an atmosphere of oxygen.[2]

K + O2 → KO2

Important reactions:

4 KO2 + 2 H2O → 4 KOH + 3 O2
4 KOH + 2 CO2 → 2 K2CO3 + 2 H2O
Combine two first reaction:
4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2

If more water and CO2 available:

2 K2CO3 + 2 CO2 + 2 H2O → 4 KHCO3
Overall Reaction:
4 KO2 + 4 CO2 + 2 H2O → 4 KHCO3 + 3 O2


The Russian Space Agency has had success using potassium superoxide in chemical oxygen generators for its spacesuits and Soyuz spacecraft. KO2 has also been utilized in canisters for rebreathers for fire fighting and mine rescue work, but had limited use in scuba rebreathers because of its dangerously explosive reaction with water. The theoretical capacity of KO2 is the absorption of 0.618 kg CO2 per kg of absorbent while 0.380 kg O2 are generated per kg of absorbent. For one KO2 molecule, it's one CO2 molecule but only 0.75 oxygen molecules. The human body though will produce less CO2 molecules than oxygen molecules needed because oxidation of food also needs oxygen to produce water and urea.


  1. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X. 
  2. ^ Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort “Peroxo Compounds, Inorganic” Ullmann's Encyclopedia of Industrial Chemistry, 2007, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_177.pub2