Potassium superoxide

Potassium superoxide
IUPAC name Potassium dioxide
Other names Potassium superoxide
Identifiers
CAS number	12030-88-5 Y
PubChem	61541
RTECS number	TT6053000
Jmol-3D images	Image 1
SMILES O=O.[K+]
InChI InChI=1S/K.O2/c;1-2/q+1;
Properties
Molecular formula	KO2
Molar mass	71.1 g mol−1
Appearance	yellow solid
Density	2.14 g/cm3, solid
Melting point	560 °C, 833 K, 1040 °F (decomp.)
Solubility in water	decomposes
Structure
Crystal structure	Body-centered cubic (O2-)
Thermochemistry
Std enthalpy of formation ΔfHo298	−283 kJ·mol−1[1]
Standard molar entropy So298	117 J·mol−1·K−1[1]
Hazards
R-phrases	8-14-34
S-phrases	17-27-36/37/39
Main hazards	corrosive, oxidant
NFPA 704	0 3 3
Related compounds
Other anions	Potassium oxide Potassium peroxide
Other cations	Sodium superoxide
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Potassium superoxide is the chemical compound with the formula KO₂. This rare salt of the superoxide ion is produced by burning molten potassium in pure oxygen. 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.

Important reactions:

4 KO₂ + 2 H₂O → 4 KOH + 3 O₂

2 KOH + CO₂ → K₂CO₃ + H₂O

K₂CO₃ + CO₂ + H₂O → 2 KHCO₃

4 KO₂ + 2 CO₂ → 2 K₂CO₃ + 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 0.309 kg CO₂ per kg of absorbent while 0.38 kg O₂ are generated per kg of absorbent.^{[citation needed]} The human body though will produce more CO₂ than oxygen absorbed, thus a device or absorbent specifically for CO₂ scrubbing may also be required.

Structural trends in dioxygen compounds

The derivatives of dioxygen, O₂, have characteristic O-O distances that correlate with the bond order of the O-O bond.

References

1. ^ ^{a b} Zumdahl, Steven S. (2009). Chemical Principles 6th Ed.. Houghton Mifflin Company. p. A22. ISBN 0-618-94690-X. 
2. ^ Abrahams, S. C.; Kalnajs, J. "The Crystal Structure of α-Potassium Superoxide" Acta Crystallographica (1955) volume 8, pages 503-506. doi:10.1107/S0365110X55001540.

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