Potassium superoxide

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Potassium superoxide
Unit cell of potassium superoxide
  Potassium cations, K+
  Superoxide anions, O−2
Names
IUPAC name
Potassium superoxide
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.031.574 Edit this at Wikidata
EC Number
  • 234-746-5
RTECS number
  • TT6053000
UN number 2466
  • InChI=1S/2K.O2/c;;1-2/q2*+1;-2 ☒N
    Key: XXQBEVHPUKOQEO-UHFFFAOYSA-N ☒N
  • InChI=1/2K.O2/c;;1-2/q2*+1;-2
    Key: XXQBEVHPUKOQEO-UHFFFAOYAV
  • [K+].[O-]=O
Properties
KO2
Molar mass 71.096 g·mol−1
Appearance yellow solid
Density 2.14 g/cm3, solid
Melting point 560 °C (1,040 °F; 833 K) (decomposes)
Hydrolysis
+3230·10−6 cm3/mol[1]
Structure
Body-centered tetragonal[2][3]
Thermochemistry
117 J/(mol·K)[4]
Std enthalpy of
formation
(ΔfH⦵298)
 −283 kJ/mol[4]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Corrosive, oxidizer, reacts violently with water
GHS labelling:[5]
GHS03: OxidizingGHS05: Corrosive
Danger
H271, H314
P210, P220, P221, P260, P264, P280, P283, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P306+P360, P310, P321, P363, P370+P378, P371+P380+P375, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 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. hydrogen peroxideSpecial hazard W+OX: Reacts with water in an unusual or dangerous manner AND is oxidizer
3
0
3
W
OX
Related compounds
Other cations
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium superoxide is an

spacesuits
.

Production and reactions

Potassium superoxide is produced by burning molten potassium in an atmosphere of excess oxygen.[7]

K + O2 → KO2

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

Reactivity

Potassium superoxide is a source of superoxide, which is an oxidant and a nucleophile, depending on its reaction partner.[8]

Upon contact with water, it undergoes disproportionation to potassium hydroxide, oxygen, and hydrogen peroxide:

4 KO2 + 2 H2O → 4 KOH + 3 O2
2 KO2 + 2 H2O → 2 KOH + H2O2 + O2[9]

It reacts with carbon dioxide, releasing oxygen:

4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2
4 KO2 + 4 CO2 + 2 H2O → 4 KHCO3 + 3 O2

Potassium superoxide finds only niche uses as a laboratory reagent. Because it reacts with water, KO2 is often studied in organic solvents. Since the salt is poorly soluble in nonpolar solvents,

diacyl peroxides.[10]

Ion exchange with tetramethylammonium hydroxide gives tetramethylammonium superoxide, a yellow solid.[11]

Applications

The

fire fighting and mine rescue work, but had limited use in scuba rebreathers because of its highly exothermic reaction with water. Potassium superoxide was used in a rudimentary life support system for five mice as part of the Biological Cosmic Ray Experiment on Apollo 17.[12]

Theoretically, 1 kg of KO2 absorbs 0.310 kg of CO2 while releasing 0.338 kg of O2. One mole of KO2 absorbs 0.5 moles of CO2 and releases 0.75 moles of oxygen.

References

  1. ^ "Handbook of Chemistry and Physics 102nd Edition". CRC Press.
  2. ^
    doi:10.1107/S0365110X55001540
    .
  3. ^ "Information card for entry 2310803". Crystallography Open Database. Retrieved 28 July 2022.
  4. ^
    ISBN 978-0-618-94690-7
    .
  5. ^ "Potassium superoxide". pubchem.ncbi.nlm.nih.gov. Retrieved 14 December 2021.
  6. PMID 26875845
    .
  7. ISBN 978-3527306732
    .
  8. ISBN 978-0471936237
    .
  9. ISBN 978-8122413847
    .
  10. ISBN 0471936235
    .
  11. doi:10.1002/0471653683.ch1
    .
  12. ^ Haymaker, Webb; Look, Bonne C.; Benton, Eugene V.; Richard C. Simmonds (1975-01-01). "The Apollo 17 pocket mouse experiment (Biocore)". Biomedical Results of Apollo. NASA-SP-368.
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