:Strontium bromide
{{Use British English|date=February 2020}}
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| ImageFile = Strontium-bromide-xtal-2011-Mercury-3D-balls.png
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| IUPACName = Strontium bromide
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|Section1={{Chembox Identifiers
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 23635
| InChI = 1S/2BrH.Sr/h2*1H;/q;;+2/p-2
| InChIKey = YJPVTCSBVRMESK-NUQVWONBAI
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2BrH.Sr/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = YJPVTCSBVRMESK-UHFFFAOYSA-L
| InChIKey1 = YJPVTCSBVRMESK-UHFFFAOYSA-L
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 10476-81-0
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 1NG558X5VJ
| EINECS = 233-969-5
| PubChem = 25302
| SMILES = [Sr+2].[Br-].[Br-]
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|Section2={{Chembox Properties
| Formula = {{chem2|SrBr2}}
| MolarMass = 247.428 g/mol (anhydrous)
355.53 g/mol (hexahydrate)
| Appearance = white crystalline powder
| Density = 4.216 g/cm3 (anhydrous)
2.386 g/cm3 (hexahydrate)
| MeltingPtC = 643
| BoilingPtC = 2146
| BoilingPt_notes =
| Solubility = 107 g/100 mL
| SolubleOther = Soluble in ethanol
Insoluble in diethyl ether
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| MagSus = −86.6·10−6 cm3/mol }}
|Section3={{Chembox Structure
| CrystalStruct = Tetragonal
| SpaceGroup = P4/n (No. 85)
| LattConst_a = 1160.42 pm
| LattConst_c = 713.06 pm
| UnitCellFormulas = 10
| Coordination =
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|Section4={{Chembox Thermochemistry
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|Section5={{Chembox Pharmacology
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|Section6={{Chembox Explosive
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|Section7={{Chembox Hazards
| MainHazards = Corrosive
| NFPA-H = 1
| NFPA-F = 0
| NFPA-R = 1
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|Section8={{Chembox Related
| OtherAnions = {{ubl|Strontium fluoride|Strontium chloride|Strontium iodide}}
| OtherCations = {{ubl|Beryllium bromide|Magnesium bromide|Calcium bromide|Barium bromide|Radium bromide}}
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Strontium bromide is a chemical compound with a formula {{chem2|SrBr2|auto=1}}. At room temperature it is a white, odourless, crystalline powder. Strontium bromide imparts a bright red colour in a flame test, showing the presence of strontium ions. It is used in flares and also has some pharmaceutical uses.
Preparation
{{chem2|SrBr2}} can be prepared from strontium hydroxide and hydrobromic acid.
:{{chem2|Sr(OH)2 + 2 HBr → SrBr2 + 2 H2O}}
Alternatively strontium carbonate can also be used as strontium source.
:{{chem2|SrCO3 + 2 HBr → SrBr2 + H2O + CO2(g)}}
These reactions give hexahydrate of strontium bromide ({{chem2|SrBr2*6H2O}}), which decomposes to dihydrate ({{chem2|SrBr2*2H2O}}) at 89 °C. At 180 °C anhydrous {{chem2|SrBr2}} is obtained.Dale L. Perry, Sidney L. Phillips: Handbook of Inorganic Compounds. CRC Press, 1995, {{ISBN|978-0-8493-8671-8}}, ({{Google books|0fT4wfhF1AsC|page=387}}).
Structure
At room temperature, strontium bromide adopts a crystal structure with a tetragonal unit cell and space group P4/n. This structure is referred to as α-{{chem2|SrBr2}} and is isostructural with europium(II) bromide and uranium diselenide. The compound's structure was initially erroneously interpreted as being of the Lead(II) chloride type,{{cite journal | last=Kamermans | first=M. A. | title=The Crystal Structure of SrBr2. | journal=Zeitschrift für Kristallographie - Crystalline Materials | publisher=Walter de Gruyter GmbH | volume=101 | issue=1–6 | date=1939-12-01 | issn=2196-7105 | doi=10.1524/zkri.1939.101.1.406 | pages=406–411| s2cid=102183214}} but this was later corrected.{{cite journal| title = The crystal structure of strontium bromide| author = R. L. Sass| journal = J. Phys. Chem. | year = 1963 | volume =67 | page = 2862| doi = 10.1021/j100806a516| issue = 12|display-authors=etal}}
Around 920 K (650 °C), α-{{chem2|SrBr2}} undergoes a first-order solid-solid phase transition to a much less ordered phase, β-{{chem2|SrBr2}}, which adopts the cubic fluorite structure. The beta phase of strontium bromide has a much higher ionic conductivity of about 1 S/cm, comparable to that of molten {{chem2|SrBr2}}, due to extensive disorder in the bromide sublattice.{{cite journal | first1 = Stephen | last1 = Hull | first2 = Stefan T. | last2 = Norberg | first3 = Istaq | last3 = Ahmed | first4 = Sten G. | last4 = Eriksson | first5 = Chris E. | last5 = Mohn | title = High temperature crystal structures and superionic properties of SrCl2, SrBr2, BaCl2 and BaBr2 | journal = J. Solid State Chem. | volume = 184 | issue = 11 | year = 2011 | pages = 2925–2935 | doi = 10.1016/j.jssc.2011.09.004 | bibcode = 2011JSSCh.184.2925H}} Strontium bromide melts at 930 K (657 °C).
File:Strontium-bromide-xtal-3D-sf.png|Space-filling model of the packing of {{chem2|Sr(2+)}} and {{chem2|Br−}} ions in α-{{chem2|SrBr2}}
File:Strontium-bromide-xtal-Sr1-coordination-view-2-3D-bs-17-25.png|Distorted square antiprismatic coordination geometry of crystallographically independent strontium atom number 1
File:Strontium-bromide-xtal-Sr2-coordination-view-2-3D-bs-17-25.png|Square antiprismatic coordination geometry of strontium number 2
File:Strontium-bromide-xtal-Br1-coordination-3D-bs-17-25.png|Flattened tetrahedral coordination geometry of bromine number 1
File:Strontium-bromide-xtal-Br2-coordination-3D-bs-17-25.png|Distorted tetrahedral coordination geometry of bromine number 2
File:Strontium-bromide-xtal-Br3-coordination-3D-bs-17-25.png|Tetrahedral coordination geometry of bromine number 3
File:Strontium-bromide-xtal-Br4-coordination-3D-bs-17-25.png| Tetrahedral coordination geometry of bromine number 4
See also
References
{{reflist}}
- http://www.webelements.com/
{{Strontium compounds}}
{{bromine compounds}}