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KO2

Potassium superoxide
Unit cell of potassium superoxide
Names
IUPAC name
Potassium dioxide
Other names
Potassium superoxide
Identifiers
3D model (Jmol)
ChemSpider
ECHA InfoCard 100.031.574
EC Number 234-746-5
PubChem CID
RTECS number TT6053000
Properties
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)
decomposes
Structure
Body-centered cubic (O−
2)
Thermochemistry
117 J·mol−1·K−1
−283 kJ·mol−1
Hazards
Main hazards corrosive, oxidant
R-phrases (outdated) 8-14-34
S-phrases (outdated) 17-27-36/37/39
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 hazard OX: Oxidizer. E.g., potassium perchlorateNFPA 704 four-colored diamond
Related compounds
Other anions
Potassium oxide
Potassium peroxide
Other cations
Sodium 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

Potassium superoxide is the inorganic compound with the formula KO
2. It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide ion. Potassium superoxide is used as a CO
2 scrubber, H
2O dehumidifier and O
2 generator in rebreathers, spacecraft, submarines and spacesuit life support systems.

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

The salt consists of K+
 and O−
2 ions, linked by ionic bonding. The O−O distance is 1.28 Å.

Hydrolysis gives oxygen gas, hydrogen peroxide and potassium hydroxide:

Its degradation by carbon dioxide affords carbonates:

Combinations of these two reactions occur as well:

Potassium superoxide finds only niche uses as a laboratory reagent. Because it reacts with water, KO
2 is often studied in organic solvents. Since the salt is poorly soluble in nonpolar solvents, crown ethers are typically used. The tetraethylammonium salt is also known. Representative reactions of these salts involve the use of superoxide as a nucleophile, e.g., in the conversion of alkyl bromides to alcohols and acyl chlorides into diacyl peroxides.


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