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Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.013.753 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 1884 |
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| Properties | |
| BaO | |
| Molar mass | 153.326 g/mol |
| Appearance | white solid |
| Density | 5.72 g/cm3, solid |
| Melting point | 1,923 °C (3,493 °F; 2,196 K) |
| Boiling point | ~ 2,000 °C (3,630 °F; 2,270 K) |
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| Solubility | soluble inethanol, dilute mineral acids and alkalies; insoluble inacetone and liquidammonia |
| −29.1·10−6 cm3/mol | |
| Structure | |
| cubic,cF8 | |
| Fm3m, No. 225 | |
| Octahedral | |
| Thermochemistry | |
| 47.7 J/K mol | |
Std molar entropy(S⦵298) | 70 J·mol−1·K−1[1] |
Std enthalpy of formation(ΔfH⦵298) | −582 kJ·mol−1[1] |
| Hazards | |
| GHS labelling: | |
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| Danger | |
| H301,H302,H314,H315,H332,H412 | |
| P210,P220,P221,P260,P261,P264,P270,P271,P273,P280,P283,P301+P310,P301+P312,P301+P330+P331,P302+P352,P303+P361+P353,P304+P312,P304+P340,P305+P351+P338,P306+P360,P310,P312,P321,P330,P332+P313,P362,P363,P370+P378,P371+P380+P375,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
Otheranions | |
Othercations | |
| Supplementary data page | |
| Barium oxide (data page) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Barium oxide, also known asbaria, is a whitehygroscopic non-flammablecompound with the formula BaO. It has acubic structure and is used incathode-ray tubes, crown glass, andcatalysts. It is harmful to human skin and if swallowed in large quantity causes irritation. Excessive quantities of barium oxide may lead to death.
It is prepared by heatingbarium carbonate withcoke,carbon black ortar or bythermal decomposition ofbarium nitrate.[citation needed]
Barium oxide is used as a coating forhot cathodes, for example, those incathode-ray tubes. It replacedlead(II) oxide in the production of certain kinds of glass such as opticalcrown glass. While lead oxide raised therefractive index, it also raised thedispersive power, which barium oxide does not alter.[2] Barium oxide also has use as anethoxylationcatalyst in the reaction ofethylene oxide andalcohols, which takes place between 150 and 200 °C.[3]
It is most known for its use in theBrin process, named after its inventors, a reaction that was used as a large scale method to produce oxygen beforeair separation became the dominant method in the beginning of the 20th century, as BaO can be a source of pure oxygen through heat fluctuation.
BaO(s) + ½O2(g) ⇌ BaO2(s)
It oxidises to BaO2 by formation of aperoxideion ([O−O]2−, orO2−2) — with the same charge ofO2−, and therefore keeping the electrochemical balance with the most stableBa2+. Using theKröger-Vink notation,
½O2(g) + O2–
O ⇌ [O
2]2–
O
where J
O is the species J in the oxygen position within the rock-salt lattice. The complete peroxidation of BaO to BaO2 occurs at moderate temperatures by oxygen uptake within the BaO rock-salt lattice:
Calculations usingDensity Functional Theory (DFT) suggest that the oxygen incorporation reaction is exothermic, and that the most energetically favoured occupation site is indeed the peroxide ion at the oxide lattice — other than interstitial positions, for instance. However, the increased entropy of the system is what leads BaO2 to decompose to BaO and release O2 between 800 and 1100 K (520 and 820 °C).[4] The reaction was used as a large scale method to produce oxygen beforeair separation became the dominant method in the beginning of the 20th century. The method was named theBrin process, after its inventors.[5]
Barium oxide from metallic barium readily forms from its exothermic oxidation withdioxygen in air:
2 Ba(s) + O2(g) → 2 BaO(s).
It's most commonly made by heatingbarium carbonate at temperatures of 1000–1450 °C.
BaCO3(s) → BaO(s) + CO2(g)
Likewise, it is often formed through the thermal decomposition of otherbarium salts,[6] likebarium nitrate.[7]
Barium oxide is anirritant. If it contacts the skin or the eyes or is inhaled it causes pain and redness. However, it is more dangerous when ingested. It can causenausea anddiarrhea,muscle paralysis, cardiac arrhythmia, and can cause death. If ingested, medical attention should be sought immediately.
Barium oxide should not be released environmentally; it is harmful toaquatic organisms.[8]
