Potassium superoxide
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| Names | |
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| IUPAC name
Potassium superoxide
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| Identifiers | |
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3D model (JSmol)
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PubChem CID
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| UN number | 2466 |
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| 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 | |
Std molar
entropy (S⦵298) |
117 J/(mol·K)[4] |
Std enthalpy of
formation (ΔfH⦵298) |
−283 kJ/mol[4] |
| Hazards | |
| NFPA 704 (fire diamond) | Page Template:NFPA 704 diamond/styles.css has no content. |
| Related compounds | |
Other cations
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Template:Chembox Footer/trackingTemplate:Short description
Potassium superoxide is an inorganic compound with the formula Page Module:Chem2/styles.css has no content.KO2.[6] It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide anion. It is used as a Page Module:Chem2/styles.css has no content.CO2 scrubber, Page Module:Chem2/styles.css has no content.H2O dehumidifier, and Page Module:Chem2/styles.css has no content.O2 generator in rebreathers, spacecraft, submarines, and spacesuits.
Production and reactions
Potassium superoxide is produced by burning molten potassium in an atmosphere of excess oxygen.[7]
- Page Module:Chem2/styles.css has no content.K + O2 → KO2
The salt consists of Page Module:Chem2/styles.css has no content.K+ and Page Module:Chem2/styles.css has no content.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:
- Page Module:Chem2/styles.css has no content.4 KO2 + 2 H2O → 4 KOH + 3 O2
- Page Module:Chem2/styles.css has no content.2 KO2 + 2 H2O → 2 KOH + H2O2 + O2[9]
It reacts with carbon dioxide, releasing oxygen:
- Page Module:Chem2/styles.css has no content.4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2
- Page Module:Chem2/styles.css has no content.4 KO2 + 4 CO2 + 2 H2O → 4 KHCO3 + 3 O2
Theoretically, 1 kg of Page Module:Chem2/styles.css has no content.KO2 absorbs 0.310 kg of CO2 while releasing 0.338 kg of Page Module:Chem2/styles.css has no content.O2. One mole of Page Module:Chem2/styles.css has no content.KO2 absorbs 0.5 moles of CO2 and releases 0.75 moles of oxygen.
As a laboratory reagent, potassium superoxide only finds niche uses. Because it reacts with water, Page Module:Chem2/styles.css has no content.KO2 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 using superoxide as a nucleophile, e.g., in converting alkyl bromides to alcohols and acyl chlorides to diacyl peroxides.[10]
Ion exchange with tetramethylammonium hydroxide gives tetramethylammonium superoxide, a yellow solid.[11]
Applications
The Russian Space Agency has successfully used potassium superoxide in chemical oxygen generators for its spacesuits and Soyuz spacecraft. Potassium superoxide was also used in a rudimentary life support system for five mice as part of the Biological Cosmic Ray Experiment on Apollo 17.[12]
Page Module:Chem2/styles.css has no content.KO2 has also been used in canisters for rebreathers for firefighting and mine rescue, and in cartridges for chemical oxygen generators on submarines. A flash fire caused by dropping such a cartridge into seawater contributed to the Kursk disaster. This highly exothermic reaction with water is also the reason why potassium superoxide has had only limited use in scuba rebreathers.
Safety
Potassium superoxide is a pressure-sensitive explosive that detonates when scratched.[13][14]
References
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- ^ Page Module:Citation/CS1/styles.css has no content."Handbook of Chemistry and Physics 102nd Edition". CRC Press.
- ^ a b Page Module:Citation/CS1/styles.css has no content.Abrahams, S. C.; Kalnajs, J. (1955). "The Crystal Structure of α-Potassium Superoxide". Acta Crystallographica. 8 (8): 503–6. Bibcode:1955AcCry...8..503A. doi:10.1107/S0365110X55001540.
- ^ Page Module:Citation/CS1/styles.css has no content."Information card for entry 2310803". Crystallography Open Database. Retrieved 28 July 2022.
- ^ a b Page Module:Citation/CS1/styles.css has no content.Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin. p. A22. ISBN 978-0-618-94690-7.
- ^ Page Module:Citation/CS1/styles.css has no content."Potassium superoxide". pubchem.ncbi.nlm.nih.gov. Retrieved 14 December 2021.
- ^ Page Module:Citation/CS1/styles.css has no content.Hayyan M.; Hashim M. A.; AlNashef I. M. (2016). "Superoxide Ion: Generation and Chemical Implications". Chem. Rev. 116 (5): 3029–3085. doi:10.1021/acs.chemrev.5b00407. PMID 26875845.
- ^ Page Module:Citation/CS1/styles.css has no content.Jakob, Harald; Leininger, Stefan; Lehmann, Thomas; Jacobi, Sylvia; Gutewort, Sven (2007). "Peroxo Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a19_177.pub2. ISBN 978-3527306732.
- ^ Page Module:Citation/CS1/styles.css has no content.Johnson, Roy A.; Adrio, Javier; Ribagorda, María (2007). "Potassium Superoxide". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rp250.pub2. ISBN 978-0471936237.
- ^ Page Module:Citation/CS1/styles.css has no content.Kumar De, Anil (2007). A Text Book of Inorganic Chemistry. New Age International. p. 247. ISBN 978-8122413847.
- ^ Page Module:Citation/CS1/styles.css has no content.Johnson, Roy A.; Adrio, Javier; Ribagorda, María (2001). "Potassium Superoxide". e-EROS Encyclopedia of Reagents for Organic Synthesis. Wiley. doi:10.1002/047084289X.rp250.pub2. ISBN 0471936235.
- ^ Page Module:Citation/CS1/styles.css has no content.Bohle, D. Scott; Sagan, Elisabeth S. (2004). "Main Group Compounds". Inorganic Syntheses. Vol. 34. p. 36. doi:10.1002/0471653683.ch1. ISBN 978-0-471-64750-8.
- ^ Page Module:Citation/CS1/styles.css has no content.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.
- ^ Page Module:Citation/CS1/styles.css has no content.Delahunt, J.; Lindeman, T. (2007). "Review of the safety of potassium and potassium oxides, including deactivation by introduction into water". Journal of Chemical Health and Safety. 14 (2): 21–32. doi:10.1016/j.jchas.2006.09.010.
- ^ Page Module:Citation/CS1/styles.css has no content.Burkhardt, Elizabeth R. (2006). "Potassium and Potassium Alloys". Ullmann's Encyclopedia of Industrial Chemistry. Vol. A22. pp. 31–38. doi:10.1002/14356007.a22_031.pub2. ISBN 978-3-527-30673-2.
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