por What is barium hydroxide?
He barium hydroxide is a chemical compound with the formula Ba(OH)2(H₂O)x. It is a strong base and can be in anhydrous, monohydrate, or octohydrate form. The monohydrated form, also called barite water, is the most common and in commercial use.
Barium hydroxide can be prepared by dissolving barium oxide (BaO) in water: BaO + 9H2O → Ba(OH)2 8H2O. It crystallizes as the octahydrate, which is converted to the monohydrate on heating in air. At 100 °C in a vacuum, the monohydrate will produce BaO and water.
Barium hydroxide properties
– Barium hydroxide are white or transparent octahedral crystals. Odorless and with a caustic taste.
– The anhydrous form has a molecular weight of 171.34 g/mol, a density of 2.18 g/ml, a melting point of 407 °C and a boiling point of 780 °C.
– The monohydrate form has a molecular weight of 189.355 g/mol, a density of 3.743 g/ml, and a melting point of 300 °C.
– The octohydrate form has a molecular weight of 315.46 g/mol, a density of 2.18 g/ml, and a melting point of 78 °C.
– The compound is slightly soluble in water and insoluble in acetone. It is a strong base with a pKa of 0.15 and 0.64 for the first and second OH– respectively.
– Barium hydroxide reacts similarly to sodium hydroxide (NaOH), but is less soluble in water.
– Neutralizes acids exothermically to form salts plus water.
– May react with aluminum and zinc to form oxides or hydroxides of the metal and generate hydrogen gas.
– Can initiate polymerization reactions in polymerizable organic compounds, especially epoxides.
– It can generate flammable and/or toxic gases with ammonium salts, nitrides, halogenated organic compounds, various metals, peroxides and hydroperoxides. Mixtures with chlorinated gums explode when heated or crushed.
– Barium hydroxide decomposes into barium oxide when heated to 800 °C. Reaction with carbon dioxide produces barium carbonate. Its highly alkaline aqueous solution undergoes neutralization reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively.
H2SO4 + Ba(OH)2 BaSO4 + 2H2O
– Reaction with hydrogen sulfide produces barium sulfide. The precipitation of many insoluble or less soluble barium salts can result from a double replacement reaction when an aqueous solution of barium hydroxide is mixed with many solutions of other metal salts.
– Mixing solid hydrated barium hydroxide with solid ammonium chloride in a beaker produces an endothermic reaction to produce a liquid, with the evolution of ammonia. The temperature drops drastically to approximately -20ºC.
Ba(OH)2 (s) + 2NH4Cl (s) → BaCl2 (aq) + 2NH3 (g) + H2O
– Ba(OH)2 reacts with carbon dioxide to produce barium carbonate. This is expressed by the following chemical reaction:
Ba(OH)2 + CO2 → BaCO3 + H2O.
Reactivity and hazards
Barium hydroxide is classified as a stable, non-combustible compound that reacts rapidly and exothermically with acids, and is incompatible with carbon dioxide and moisture. The compound is toxic and, as a strong base, it is corrosive.
Inhalation, ingestion, or skin contact with material can cause serious injury or death. Contact with the molten substance can cause severe burns to the skin and eyes.
Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Fire control wastewater can be corrosive and/or toxic and cause contamination.
Eye contact
If the compound comes into contact with the eyes, check and remove contact lenses. Immediately flush eyes with plenty of water for at least 15 minutes, using cold water.
Skin contact
In case of skin contact, the affected area should be rinsed immediately for at least 15 minutes with plenty of water or a weak acid, eg vinegar, while removing contaminated clothing and shoes.
Wash clothing and shoes before reuse. If contact is severe, wash with disinfectant soap and cover contaminated skin with antibacterial cream.
Inhalation
In case of inhalation, the victim should be moved to a cool place. If he is not breathing, artificial respiration is given. If breathing is difficult, give oxygen.
Ingestion
If the compound is swallowed, do not induce vomiting. Loosen tight clothing such as a shirt collar, belt, or tie.
In all cases immediate medical attention should be obtained.
Applications
1. Industry
– Barium hydroxide is used as a precursor for other barium compounds. The monohydrate is used to dehydrate and remove sulfate from various products. This industrial application also applies to laboratory uses.
– It is used as an additive in thermoplastics (such as phenolic resins), scratches and PVC stabilizers to improve plastic properties. This material is used as a general purpose additive for lubricants and greases.
– Other industrial applications include the manufacture of sugar, soaps, saponification of fats, melting of silicates, and chemical synthesis of other barium compounds and organic compounds.
2. Laboratory
– It 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, since barium carbonate is insoluble in water.
This allows indicators such as phenolphthalein or thymophtalein (with alkaline color changes) to be used without risk of titration errors caused by the presence of carbonate ions, which are much less basic.
– It is occasionally used in organic synthesis as a strong base, for example for the hydrolysis of esters and nitriles.
– It is also used in the decarboxylation of amino acids that release barium carbonate in the process.
– It is also used in the preparation of cyclopentanone, diacetone alcohol and gamma-lactone D-Gulonica.
3. Catalyst in the Wittig-Horner reaction
The Wittig-Horner reaction, also known as the Horner-Wadsworth-Emmons reaction (or HWE reaction) is a chemical reaction used in organic chemistry to stabilize carbanions of phosphonates with aldehydes (or ketones) to produce predominantly E-alkenes (trans ).
The Wittig-Horner soncochemical reaction is catalyzed by activated barium hydroxide and is carried out under solid-liquid interface conditions.
The soncochemical process takes place at room temperature and with a lower catalyst weight and reaction time than the thermal process. Under these conditions, yields similar to those of the thermal process are obtained.
The nature of the active site of the catalyst that acts in the process is analyzed. An ETC mechanism is proposed for the soncochemical process.
4. Other uses
Barium hydroxide has other uses, such as:
– The manufacture of alkali.
– The construction of glass.
– Vulcanization of synthetic rubber.
– Corrosion inhibitors.
– Like drilling fluids, pesticides and lubricants.
– For the boiler remedy.
– To refine vegetable and animal oils.
– For fresco painting.
– In the softening of water.
– As an ingredient in homeopathic remedies.
– To clean up acid spills.
– It is also used in the sugar industry to prepare beet sugar.
– Construction materials.
– Electrical and electronic products.
– Floor coverings.
References
Barium Hydroxide (SF). Retrieved from chemistrylearner.com.
BARIUM HYDROXIDE (SF). Recovered from chemicalland21.com.