Barium hydroxide

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Barium hydroxide
Identifiers
CAS number 17194-00-2 YesY
22326-55-2 (monohydrate)
12230-71-6 (octahydrate)
PubChem 28387
ChemSpider 26408 YesY
ChEBI CHEBI:32592 YesY
RTECS number CQ9200000
Jmol-3D images Image 1
Properties
Molecular formula Ba(OH)2
Molar mass 171.34 g/mol (anhydrous)
189.39 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearance white solid
Density 3.743 g/cm3 (monohydrate)
2.18 g/cm3 (octahydrate, 16 °C)
Melting point 78 °C (octahydrate)
300°C (monohydrate)
407 °C (anhydrous)
Boiling point 780 °C
Solubility in water octahydrate:
1.67 g/100 mL (0 °C)
3.89 g/100 mL (20 °C)
11.7 g/100 mL (50 °C)
20.94 g/100 mL (60 °C)
101.4 g/100 mL (100 °C)
Solubility in other solvents low
Basicity (pKb) -2.02
Refractive index (nD) 1.50 (octahydrate)
Structure
Crystal structure octahedral
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−944.7 kJ/mol
Hazards
MSDS External MSDS
EU Index 056-002-00-7
EU classification Harmful (Xn)
R-phrases R20/22
S-phrases (S2), S28
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions Barium oxide
Barium peroxide
Other cations Calcium hydroxide
Strontium hydroxide
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Barium hydroxide is the chemical compound with the formula Ba(OH)2. Also known as baryta, or baryta-water, it is one of the principal compounds of barium. The white granular monohydrate is the usual commercial form.

Preparation[edit]

Barium hydroxide can be prepared by dissolving barium oxide (BaO) in water:

BaO + 9 H2O → Ba(OH)2·8H2O

It crystallises as the octahydrate, which converts to the monohydrate upon heating in air. At 100 °C in a vacuum, the monohydrate gives BaO.[1]

Uses[edit]

Barium hydroxide is used in analytical chemistry for the titration of weak acids, particularly organic acids. Its clear aqueous solution is guaranteed to be free of carbonate, unlike those of sodium hydroxide and potassium hydroxide, as barium carbonate is insoluble in water. This allows the use of indicators such as phenolphthalein or thymolphthalein (with alkaline colour changes) without the risk of titration errors due to the presence of carbonate ions, which are much less basic.[2]

Barium hydroxide is used in organic synthesis as a strong base, for example for the hydrolysis of esters[3] and nitriles.[4][5][6]

Barium hydroxide-catalyzed 2-carboxy-1,3-dihydroxynaphthalene preparation.svg
Barium hydroxide-catalyzed methylsuccinic acid preparation.svg

It has been used to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate.[7]

Barium hydroxide is used, as well, in the decarboxylation of amino acids liberating barium carbonate in the process. [8]

It is also used in the preparation of cyclopentanone,[9] diacetone alcohol[10] and D-Gulonic γ-lactone.[11]

Barium hydroxide-catalyzed diacetone alcohol preparation.svg

Miscellaneous applications[edit]

  • It is also used to clean up acid spills.
  • It is also used to neutralize sulfuric acid solutions. Use of Ba(OH)2 is particularly beneficial in complete removal sulphate ions because the BaSO4 formed is insoluble in water and precipitates out.

Reactions[edit]

Barium hydroxide decomposes to barium oxide when heated to 800 °C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkaline, undergoes neutralization reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double replacement reaction when a barium hydroxide aqueous solution is mixed with many solutions of other metal salts. [12]

Reactions of barium hydroxide with ammonium salts are strongly endothermic. The reaction of barium hydroxide octahydrate with ammonium chloride[13] [14] or[15] ammonium thiocyanate[15][16] is often used as a classroom chemistry demonstration, producing temperatures cold enough to freeze water and enough water to dissolve the resulting mixture.

Safety[edit]

Barium hydroxide presents the same hazards as other strong bases and as other water-soluble barium compounds: it is corrosive and toxic.

See also[edit]

References[edit]

  1. ^ (1960). Gmelins Handbuch der anorganischen Chemie (8. Aufl.), Weinheim: Verlag Chemie, p. 289.
  2. ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), New York: Prentice Hall, ISBN 0-582-22628-7 
  3. ^ Meyer, K.; Bloch, H. S. (1945). "Naphthoresorcinol". Org. Synth. 25: 73; Coll. Vol. 3: 637.
  4. ^ Brown, G. B. (1946). "Methylsuccinic acid". Org. Synth. 26: 54; Coll. Vol. 3: 615.
  5. ^ Ford, Jared H. (1947). "β-Alanine". Org. Synth. 27: 1; Coll. Vol. 3: 34.
  6. ^ Anslow, W. K.; King, H.; Orten, J. M.; Hill, R. M. (1925). "Glycine". Org. Synth. 4: 31; Coll. Vol. 1: 298.
  7. ^ Durham, L. J.; McLeod, D. J.; Cason, J. (1958). "Methyl hydrogen hendecanedioate". Org. Synth. 38:55; Coll. Vol. 4:635.
  8. ^ [1]
  9. ^ Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Org. Synth. 5: 37; Coll. Vol. 1: 192.
  10. ^ Conant, J. B.; Tuttle, Niel. (1921). "Diacetone alcohol". Org. Synth. 1: 45; Coll. Vol. 1: 199.
  11. ^ Karabinos, J. V. (1956). "D-Gulonic γ-lactone". Org. Synth. 36: 38; Coll. Vol. 4: 506.
  12. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  13. ^ "Endothermic Reactions of Hydrated Barium Hydroxide and Ammonium Chloride". UC San Diego. Retrieved 2 April 2014. 
  14. ^ Endothermic Solid-Solid Reactions
  15. ^ a b Camp, Eric. "Endothermic Reaction". Univertist of Washington. Retrieved 2 April 2014. 
  16. ^ "Endothermic solid-solid reactions". Classic Chemistry Demonstrations. The Royal Society of Chemistry. Retrieved 2 April 2014. 

External links[edit]