Barium hydroxide
| Barium hydroxide | ||
|---|---|---|
| Identifiers | ||
| CAS number | 17194-00-2  , 22326-55-2 (monohydrate) 12230-71-6 (octahydrate) | |
| PubChem | 28387 | |
| ChemSpider | 26408 | |
| ChEBI | CHEBI:32592 | |
| RTECS number | CQ9200000 | |
| Jmol-3D images | {{#if:[Ba+2].[OH-].[OH-]|Image 1 | |
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| 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 ΔfH |
−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 |
 0
3
0
| |
| 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 | |
(verify) (what is: / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | ||
| Infobox references | ||
Barium hydroxide is the chemical compound with the formula Ba(OH)2. Also known as baryta, it is one of the principal compounds of barium. The white granular monohydrate is the usual commercial form.
Preparation
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
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]
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 is used in a demonstration of endothermic reactions since, when mixed with an ammonium salt, the reaction becomes cold as heat is absorbed from the surroundings.
Miscellaneous applications
- 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
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]
Safety
Barium hydroxide presents the same hazards as other strong bases and as other water-soluble barium compounds: it is corrosive and toxic.
See also
References
- ↑ (1960). Gmelins Handbuch der anorganischen Chemie (8. Aufl.), Weinheim: Verlag Chemie, p. 289.
- ↑ 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
- ↑ Meyer, K.; Bloch, H. S. (1945). "Naphthoresorcinol". Org. Synth. 25: 73; Coll. Vol. 3: 637.
- ↑ Brown, G. B. (1946). "Methylsuccinic acid". Org. Synth. 26: 54; Coll. Vol. 3: 615.
- ↑ Ford, Jared H. (1947). "β-Alanine". Org. Synth. 27: 1; Coll. Vol. 3: 34.
- ↑ Anslow, W. K.; King, H.; Orten, J. M.; Hill, R. M. (1925). "Glycine". Org. Synth. 4: 31; Coll. Vol. 1: 298.
- ↑ Durham, L. J.; McLeod, D. J.; Cason, J. (1958). "Methyl hydrogen hendecanedioate". Org. Synth. 38:55; Coll. Vol. 4:635.
- ↑
- ↑ Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Org. Synth. 5: 37; Coll. Vol. 1: 192.
- ↑ Conant, J. B.; Tuttle, Niel. (1921). "Diacetone alcohol". Org. Synth. 1: 45; Coll. Vol. 1: 199.
- ↑ Karabinos, J. V. (1956). "D-Gulonic γ-lactone". Org. Synth. 36: 38; Coll. Vol. 4: 506.
- ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
External links
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