Potassium oxide
 | |
| Names | |
|---|---|
| IUPAC name
Potassium oxide | |
| Systematic IUPAC name
Potassium oxidopotassium | |
| Other names
Dipotassium monoxide, Potash | |
| Identifiers | |
12136-45-7  | |
| ChemSpider | 23354117 |
| EC-number | 235-227-6 |
| |
| Jmol-3D images | Image |
| MeSH | Potassium+oxide |
| |
| UNII | 58D606078H |
| Properties | |
| Molecular formula |
K2O |
| Molar mass | 94.20 g·mol−1 |
| Appearance | Pale yellow solid |
| Odor | Odorless |
| Density | 2.32 g/cm3 (20 °C)[1] 2.13 g/cm3 (24 °C)[2] |
| Melting point | 740 °C (1,360 °F; 1,010 K) [2] decomposes from 300 °C[1] |
| Reacts[1] forming KOH | |
| Solubility | Soluble in EtOH, ether[2] |
| Structure | |
| Crystal structure | Antifluorite cubic, cF12[3] |
| Space group | Fm3m, No. 225[3] |
| Lattice constant | a = 6.436 Å[3] |
| Lattice constant | α = 90°, β = 90°, γ = 90° |
| Tetrahedral (K+) Cubic (O2−) | |
| Thermochemistry | |
| Specific heat capacity (C) |
83.62 J/mol·K[4] |
| Std molar entropy (S |
94.03 J/mol·K[4] |
| Std enthalpy of formation (ΔfH |
−363.17 kJ/mol[1][4] |
| Gibbs free energy (ΔfG˚) |
−322.1 kJ/mol[1] |
| Hazards | |
| MSDS | ICSC 0769 |
| Main hazards | Corrosive, reacts violently with water |
| Related compounds | |
| Other anions |
Potassium sulfide |
| Other cations |
Lithium oxide Sodium oxide Rubidium oxide Caesium oxide |
| Potassium peroxide Potassium superoxide | |
| Related compounds |
Potassium hydroxide |
| Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
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| Infobox references | |
Potassium oxide (K2O) is an ionic compound of potassium and oxygen. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound. Some materials of commerce, such as fertilizers and cements, are assayed assuming the percent composition that would be equivalent to K2O.
Production
Potassium oxide is produced from the reaction of oxygen and potassium; this reaction affords potassium oxide, K2O. Treatment of the peroxide with potassium produces the oxide:[5]
- K2O2 + 2 K → 2 K2O
Alternatively and more conveniently, K2O is synthesized by heating potassium nitrate with metallic potassium:
- 2 KNO3 + 10 K → 6 K2O + N2
Potassium hydroxide cannot be further dehydrated to the oxide but it can react with molten potassium to produce it, releasing hydrogen as a byproduct.
Properties and reactions
K2O crystallises in the antifluorite structure. In this motif the positions of the anions and cations are reversed relative to their positions in CaF2, with potassium ions coordinated to 4 oxide ions and oxide ions coordinated to 8 potassium.[6][7] K2O is a basic oxide and reacts with water violently to produce the caustic potassium hydroxide. It is deliquescent and will absorb water from the atmosphere, initiating this vigorous reaction.
Term use in industry
The chemical formula K2O (or simply 'K') is used in several industrial contexts: the N-P-K numbers for fertilizers, in cement formulas, and in glassmaking formulas. Although K2O is the correct formula for potassium oxide, potassium oxide is not used directly in these products. Normally potassium carbonate or some other potassium compound is used. For example, potassium oxide is about 83% potassium by weight, while potassium chloride is only 52%. Potassium chloride provides less potassium than an equal amount of potassium oxide. Thus, if a fertilizer is 30% potassium chloride by weight, its standard potassium rating, based on potassium oxide, would be only 18.8%.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Anatolievich, Kiper Ruslan. "potassium oxide". http://chemister.ru''. Retrieved 2014-07-04.
- ↑ 2.0 2.1 2.2 Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
- ↑ 3.0 3.1 3.2 Wyckoff, Ralph W.G. (1935). The Structure of Crystals. American Chemical Society (2nd ed.) (Reinhold Publishing Corp.). p. 25.
- ↑ 4.0 4.1 4.2 Dipotassium oxide in Linstrom, P.J.; Mallard, W.G. (eds.) NIST Chemistry WebBook, NIST Standard Reference Database Number 69. National Institute of Standards and Technology, Gaithersburg MD. http://webbook.nist.gov (retrieved 2014-07-04)
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ↑ Zintl, E.; Harder, A.; Dauth B. (1934). "Gitterstruktur der oxyde, sulfide, selenide und telluride des lithiums, natriums und kaliums". Zeitschrift für Elektrochemie und Angewandte Physikalische Chemie 40: 588–93.
- ↑ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
External links
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