Barium hydroxide

Last updated
Barium hydroxide
Ba(OH)2monohydrate.tif
Ba(OH)2 octahydrate.JPG
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.037.470 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 241-234-5
846955
PubChem CID
RTECS number
  • CQ9200000
UNII
  • InChI=1S/Ba.2H2O/h;2*1H2/q+2;;/p-2 Yes check.svgY
    Key: RQPZNWPYLFFXCP-UHFFFAOYSA-L Yes check.svgY
  • InChI=1/Ba.2H2O/h;2*1H2/q+2;;/p-2
    Key: RQPZNWPYLFFXCP-NUQVWONBAR
  • [Ba+2].[OH-].[OH-]
Properties
Ba(OH)2
Molar mass 171.34 g/mol (anhydrous)
189.355 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearancewhite solid
Density 3.743 g/cm3 (monohydrate)
2.18 g/cm3 (octahydrate, 16 °C)
Melting point 78 °C (172 °F; 351 K) (octahydrate)
300 °C (monohydrate)
407 °C (anhydrous)
Boiling point 780 °C (1,440 °F; 1,050 K)
mass of BaO (not Ba(OH)2):
1.67 g/100 mL (0 °C)
3.89 g/100 mL (20 °C)
4.68 g/100 mL (25 °C)
5.59 g/100 mL (30 °C)
8.22 g/100 mL (40 °C)
11.7 g/100 mL (50 °C)
20.94 g/100 mL (60 °C)
101.4 g/100 mL (100 °C)[ citation needed ]
Solubility in other solventslow
Basicity (pKb)0.15 (first OH), 0.64 (second OH) [1]
−53.2·10−6 cm3/mol
1.50 (octahydrate)
Structure
octahedral
Thermochemistry [2]
944.7 kJ·mol−1
Enthalpy of fusion fHfus)
16 kJ·mol−1
Hazards
GHS labelling:
GHS-pictogram-acid.svg GHS-pictogram-exclam.svg
Danger
H302, H314, H332, H412
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
3
1
1
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
308 mg/kg (rat, oral)
Safety data sheet (SDS) Fisher Scientific
Related compounds
Other anions
Barium oxide
Barium peroxide
Other cations
Calcium hydroxide
Strontium hydroxide
Supplementary data page
Barium hydroxide (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Barium hydroxide is a chemical compound with the chemical formula Ba(OH)2. The monohydrate (x = 1), known as baryta or baryta-water, is one of the principal compounds of barium. This white granular monohydrate is the usual commercial form.

Contents

Preparation and structure

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

BaO + H2O → Ba(OH)2

It crystallises as the octahydrate, which converts to the monohydrate upon heating in air. At 100 °C in a vacuum, the monohydrate will yield BaO and water. [3] The monohydrate adopts a layered structure (see picture above). The Ba2+ centers adopt a square antiprismatic geometry. Each Ba2+ center is bound by two water ligands and six hydroxide ligands, which are respectively doubly and triply bridging to neighboring Ba2+ centre sites. [4] In the octahydrate, the individual Ba2+ centers are again eight coordinate but do not share ligands. [5]

Coordination sphere about an individual barium ion in Ba(OH)2.H2O. Ba(OH)2O2HCoordSph.tif
Coordination sphere about an individual barium ion in Ba(OH)2.H2O.

Uses

Industrially, barium hydroxide is used as the precursor to other barium compounds. The monohydrate is used to dehydrate and remove sulfate from various products. [6] This application exploits the very low solubility of barium sulfate. This industrial application is also applied to laboratory uses.

Laboratory uses

Barium hydroxide is used in analytical chemistry for the titration of weak acids, particularly organic acids. Its aqueous solution, if clear, 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. [7]

Barium hydroxide is occasionally used in organic synthesis as a strong base, for example for the hydrolysis of esters [8] and nitriles, [9] [10] [11] and as a base in aldol condensations.

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

There are several uses for barium hydroxide such as to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate. [12]

Barium hydroxide has also been used, as well, in the decarboxylation of amino acids liberating barium carbonate in the process. [13]

It is also used in the preparation of cyclopentanone, [14] diacetone alcohol [15] and D-gulonic γ-lactone. [16]

Cyclopentanone prepn.png
Barium hydroxide-catalyzed diacetone alcohol preparation.svg

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. It is especially useful on reactions that require the titrations of weak organic 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. [17]

Reactions of barium hydroxide with ammonium salts are strongly endothermic. The reaction of barium hydroxide octahydrate with ammonium chloride [18] [19] or [20] ammonium thiocyanate [20] [21] is often used as a classroom chemistry demonstration, producing temperatures cold enough to freeze water and enough water to dissolve the resulting mixture.

Safety

Barium hydroxide presents the same hazards such as skin irritation and burns as well as eye damage, just as the other strong bases and as other water-soluble barium compounds: it is corrosive and toxic. [ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Barium</span> Chemical element, symbol Ba and atomic number 56

Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.

<span class="mw-page-title-main">Alkaline earth metal</span> Group of chemical elements

The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The elements have very similar properties: they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure.

<span class="mw-page-title-main">Sodium hydroxide</span> Chemical compound with formula NaOH

Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na+ and hydroxide anions OH.

<span class="mw-page-title-main">Base (chemistry)</span> Type of chemical substance

In chemistry, there are three definitions in common use of the word "base": Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. Rouelle in the mid-18th century.

<span class="mw-page-title-main">Sodium carbonate</span> Chemical compound

Sodium carbonate is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ashes of these sodium-rich plants were noticeably different from ashes of wood, sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process, as well as by carbonating sodium hydroxide which is made using the Chlor-alkali process.

<span class="mw-page-title-main">Copper(II) sulfate</span> Chemical compound

Copper(II) sulfate, also known as copper sulphate, is an inorganic compound with the chemical formula CuSO4. It forms hydrates CuSO4·nH2O, where n can range from 1 to 7. The pentahydrate (n = 5), a bright blue crystal, is the most commonly encountered hydrate of copper(II) sulfate, while its anhydrous form is white. Older names for the pentahydrate include blue vitriol, bluestone, vitriol of copper, and Roman vitriol. It exothermically dissolves in water to give the aquo complex [Cu(H2O)6]2+, which has octahedral molecular geometry. The structure of the solid pentahydrate reveals a polymeric structure wherein copper is again octahedral but bound to four water ligands. The Cu(II)(H2O)4 centers are interconnected by sulfate anions to form chains.

<span class="mw-page-title-main">Neutralization (chemistry)</span> Chemical reaction in which an acid and a base react quantitatively

In chemistry, neutralization or neutralisation is a chemical reaction in which acid and a base react with an equivalent quantity of each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution. The pH of the neutralized solution depends on the acid strength of the reactants.

<span class="mw-page-title-main">Barium chloride</span> Chemical compound

Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is a white powder, highly toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting to the dihydrate BaCl2·2H2O, which are colourless crystals with a bitter salty taste. It has limited use in the laboratory and industry.

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<span class="mw-page-title-main">Hexafluorosilicic acid</span> Octahedric silicon compound

Hexafluorosilicic acid is an inorganic compound with the chemical formula H
2
SiF
6
. Aqueous solutions of hexafluorosilicic acid consist of salts of the cation and hexafluorosilicate anion. These salts and their aqueous solutions are colorless.

The Kjeldahl method or Kjeldahl digestion (Danish pronunciation:[ˈkʰelˌtɛˀl]) in analytical chemistry is a method for the quantitative determination of a sample's organic nitrogen plus ammonia/ammonium. (NH3/NH4+). Without modification, other forms of inorganic nitrogen, for instance nitrate, are not included in this measurement. Using an empirical relation between Kjeldahl nitrogen and protein, it is an important method for indirectly quantifying protein content of a sample. This method was developed by Johan Kjeldahl in 1883.

<span class="mw-page-title-main">Barium chromate</span> Chemical compound

Barium chromate, is a yellow sand like powder with the formula BaCrO4. It is a known oxidizing agent and produces a green flame when heated, a result of the barium ions.

<span class="mw-page-title-main">Barium oxalate</span> Chemical compound

Barium oxalate is a chemical compound with the chemical formula BaC2O4. It is a barium salt of oxalic acid. It consists of barium cations Ba2+ and oxalate anions C2O2−4. It is a white odorless powder that is sometimes used as a green pyrotechnic colorant generally in specialized pyrotechnic compositions containing magnesium metal powder. Flame color is rich and vivid without additional chlorine donors. Such compositions burn rate is satisfied without commonly used oxidizers as nitrates, chlorates and perchlorates.

<span class="mw-page-title-main">Thermometric titration</span>

A thermometric titration is one of a number of instrumental titration techniques where endpoints can be located accurately and precisely without a subjective interpretation on the part of the analyst as to their location. Enthalpy change is arguably the most fundamental and universal property of chemical reactions, so the observation of temperature change is a natural choice in monitoring their progress. It is not a new technique, with possibly the first recognizable thermometric titration method reported early in the 20th century. In spite of its attractive features, and in spite of the considerable research that has been conducted in the field and a large body of applications that have been developed; it has been until now an under-utilized technique in the critical area of industrial process and quality control. Automated potentiometric titration systems have pre-dominated in this area since the 1970s. With the advent of cheap computers able to handle the powerful thermometric titration software, development has now reached the stage where easy to use automated thermometric titration systems can in many cases offer a superior alternative to potentiometric titrimetry.

<span class="mw-page-title-main">Barium chlorate</span> Chemical compound

Barium chlorate, Ba(ClO3)2, is the barium salt of chloric acid. It is a white crystalline solid, and like all soluble barium compounds, irritant and toxic. It is sometimes used in pyrotechnics to produce a green color. It also finds use in the production of chloric acid.

<span class="mw-page-title-main">Barium ferrate</span> Chemical compound

Barium ferrate is the chemical compound of formula BaFeO4. This is a rare compound containing iron in the +6 oxidation state. The ferrate(VI) ion has two unpaired electrons, making it paramagnetic. It is isostructural with BaSO4, and contains the tetrahedral [FeO4]2− anion.

Barium perchlorate is a powerful oxidizing agent, with the formula Ba(ClO4)2. It is used in the pyrotechnic industry.

<span class="mw-page-title-main">Tetraethylammonium chloride</span> Chemical compound

Tetraethylammonium chloride (TEAC) is a quaternary ammonium compound with the chemical formula [N(CH2CH3)4]+Cl, sometimes written as [NEt4]Cl. In appearance, it is a hygroscopic, colorless, crystalline solid. It has been used as the source of tetraethylammonium ions in pharmacological and physiological studies, but is also used in organic chemical synthesis.

References

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  15. Conant, J. B.; Tuttle, Niel. (1921). "Diacetone alcohol". Org. Synth. 1: 45; Coll. Vol.1: 199.
  16. Karabinos, J. V. (1956). "γ-lactone". Org. Synth. 36: 38; Coll. Vol.4: 506.
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  18. "Endothermic Reactions of Hydrated Barium Hydroxide and Ammonium Chloride". UC San Diego. Retrieved 2 April 2014.
  19. Endothermic Solid-Solid Reactions
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