Editing Potassium oxide

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 448711409
| ImageFile = Potassium-oxide-powder.png
| ImageFile1 = Potassium-oxide-3D-vdW.png
| ImageName = Potassium Oxide spacefilling model
| IUPACName = potassium oxide
| SystematicName = potassium oxidopotassium
| OtherNames = [[potash]], dipotassium oxide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 12136-45-7
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 23354117 
| ChemSpiderID_Comment = 
| ChEBI = 88321
| EC_number = 235-227-6
| PubChem = 25520
| UNNumber = 2033
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 58D606078H
| MeSHName = Potassium+oxide
| SMILES = O([K])[K]
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/2K.O
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = NOTVAPJNGZMVSD-UHFFFAOYSA-N
  }}
|Section2={{Chembox Properties
| K=2 | O=1
| Appearance = Pale yellow solid
| Odor = Odorless
| Density = 2.32 g/cm<sup>3</sup> (20 °C)<ref name=chemister>{{cite web|last = Anatolievich|first = Kiper Ruslan|website=chemister.ru|url = http://chemister.ru/Database/properties-en.php?dbid=1&id=516|title = potassium oxide|access-date = 2014-07-04}}</ref><br> 2.13 g/cm<sup>3</sup> (24 °C)<ref name=crc />
| Solubility = Reacts<ref name=chemister /> forming [[Potassium hydroxide|KOH]]
| SolubleOther = Soluble in [[diethyl ether]]<ref name=crc />
| MeltingPtC = 740
| MeltingPt_ref = <ref name=crc>{{CRC90}}</ref>
  }}
|Section3={{Chembox Structure
| CrystalStruct = [[Antifluorite]] [[cubic crystal system|cubic]], [[pearson symbol|cF12]]<ref name=socacs>{{cite book|page = 25|title = The Structure of Crystals|edition = 2nd|year = 1935|last = Wyckoff|first = Ralph W.G.|publisher = Reinhold Publishing Corp.|work = American Chemical Society}}</ref>
| SpaceGroup = Fm{{overline|3}}m, No. 225<ref name=socacs />
| Coordination = Tetrahedral (K<sup>+</sup>)<br> Cubic (O<sup>2−</sup>)
| LattConst_a = 6.436&nbsp;Å<ref name=socacs />
| LattConst_alpha = 90
  }}
|Section4={{Chembox Thermochemistry
| DeltaHf = −363.17 kJ/mol<ref name=chemister /><ref name=nist>{{nist|name=Dipotassium oxide|id=12136457|accessdate=2014-07-04|mask=FFFF|units=SI}}</ref>
| Entropy = 94.03 J/mol·K<ref name=nist />
| HeatCapacity = 83.62 J/mol·K<ref name=nist />
| DeltaGf = −322.1 kJ/mol<ref name=chemister />
  }}
|Section7={{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0769.htm ICSC 0769]
| MainHazards = Corrosive, reacts violently with water
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 1
| NFPA-S = W
| GHSPictograms = {{GHS05}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314}}
| PPhrases = {{P-phrases|260|264|280|301+330+331|303+361+353|304+340|305+351+338|310|321|363|405|501}}
  }}
|Section8={{Chembox Related
| OtherAnions = [[Potassium sulfide]]<br>[[Potassium selenide]]<br>[[Potassium telluride]]<br>[[Potassium polonide]]
| OtherCations = [[Lithium oxide]]<br> [[Sodium oxide]]<br> [[Rubidium oxide]]<br> [[Caesium oxide]]
| OtherFunction = [[Potassium peroxide]]<br> [[Potassium superoxide]]<br>[[Potassium ozonide]]
| OtherFunction_label = [[potassium]] [[oxide]]s
| OtherCompounds = [[Potassium hydroxide]]
  }}
}}

'''Potassium oxide''' ([[Potassium|K{{sub|2}}]][[Oxide|O]]) is an ionic [[Chemical compound|compound]] of [[potassium]] and [[oxygen]]. It is a [[Base (chemistry)|base]]. This pale yellow solid is the simplest oxide of potassium. It is a highly reactive compound that is rarely encountered.  Some industrial materials, such as fertilizers and cements, are assayed assuming the percent composition that would be equivalent to  K<sub>2</sub>O.

==Production==
Potassium oxide is produced from the reaction of oxygen and potassium; this reaction affords [[potassium peroxide]], K<sub>2</sub>O<sub>2</sub>.  Treatment of the peroxide with potassium produces the oxide:<ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. {{ISBN|0-12-352651-5}}.</ref>
:{{Chem2 | K2O2 + 2 K -> 2 K2O }}

Alternatively and more conveniently, K<sub>2</sub>O is synthesized by heating [[potassium nitrate]] with metallic potassium:
:{{Chem2 | 2 KNO3 + 10 K -> 6 K2O + N2 ↑}}

Other possibility is to heat potassium peroxide at 500&nbsp;°C which decomposes at that temperature giving pure potassium oxide and oxygen.

:{{Chem2 | 2 K2O2 -> 2 K2O + O2 ↑ }}

[[Potassium hydroxide]] cannot be further dehydrated to the oxide but it can react with molten potassium to produce it, releasing [[hydrogen]] as a byproduct.

:{{Chem2 | 2 KOH + 2 K <-> 2 K2O + H2 ↑ }}

==Properties and reactions==
K<sub>2</sub>O crystallises in the [[Fluorite structure|
 antifluorite structure]].  In this motif the positions of the [[anion]]s and [[cation]]s are reversed relative to their positions in [[calcium fluoride|CaF<sub>2</sub>]], with potassium ions coordinated to 4 oxide ions and oxide ions coordinated to 8 potassium.<ref>{{cite journal|title = Gitterstruktur der oxide, sulfide, selenide und telluride des lithiums, natriums und kaliums|journal = Zeitschrift für Elektrochemie und Angewandte Physikalische Chemie|year = 1934|volume = 40|pages = 588–93|last1 = Zintl|first1 = E.|last2 = Harder|first2 = A.|author3 = Dauth B.| issue=8 | doi=10.1002/bbpc.19340400811 |author-link1 = Eduard Zintl}}</ref><ref>Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. {{ISBN|0-19-855370-6}}.</ref> K<sub>2</sub>O 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 K<sub>2</sub>O (or simply 'K') is used in several industrial contexts: the [[N-P-K]] numbers for [[fertilizer]]s, in [[cement chemist notation|cement formulas]], and in [[glass batch calculation|glassmaking formulas]]. Potassium oxide is often not used directly in these products, but the amount of potassium is reported in terms of the K<sub>2</sub>O equivalent for whatever type of [[potash]] was used, such as [[potassium carbonate]]. 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==
{{reflist}}

==External links==
{{Commons category inline|Potassium oxide}}

{{Potassium compounds}}
{{Oxides}}

[[Category:Oxides]]
[[Category:Potassium compounds]]
[[Category:Deliquescent materials]]
[[Category:Fluorite crystal structure]]