CALCIUM HYDRIDE

CALCIUM HYDRIDE Chemical Properties
Melting point 816 °C (lit.)
density 1.9
storage temp. Store below +30°C.
form powder
color Light gray
Specific Gravity1.9
Water Solubility Soluble in water and alcohol. Insoluble in benzene.
Sensitive Moisture Sensitive
Merck 14,1672
Stability:Stable, but reacts violently with water, liberating and igniting hydrogen. Contact with strong oxidizers may cause fire or explosion. Incompatible with strong oxidizing agents, strong acids, halogens, water, alcohols.
InChIKeyFAQLAUHZSGTTLN-UHFFFAOYSA-N
CAS DataBase Reference7789-78-8(CAS DataBase Reference)
NIST Chemistry Referencecalcium hydride(7789-78-8)
EPA Substance Registry SystemCalcium hydride (CaH2) (7789-78-8)
Safety Information
Hazard Codes F
Risk Statements 15
Safety Statements 24/25-43-7/8-43A
RIDADR UN 1404 4.3/PG 1
WGK Germany 1
TSCA Yes
HazardClass 4.3
PackingGroup I
HS Code 28500090
Hazardous Substances Data7789-78-8(Hazardous Substances Data)
MSDS Information
ProviderLanguage
SigmaAldrich English
ACROS English
ALFA English
CALCIUM HYDRIDE Usage And Synthesis
Alkaline earth metalCalcium hydride is an alkaline earth metal hydride, although it is not stable than lithium hydride, but stable than other alkali metal borohydride. Chemical formula is CaH2. Molecular weight is 42.10. It is white monoclinic crystals or lumps. Industrial is gray. When exposed to moist air hydrogen will release, and calcium hydroxide will leave. The proportion of is 1.9. The decomposition tempreture is about 600℃. Melting point is 816℃ (hydrogen). When meet water, carboxylic acids, lower alcohols, it can decompose to generate hydrogen. The decomposition When tempreture get 600℃, it begins to decompose. At room temperature, it can not react with dry oxygen, nitrogen, chlorine, but can react at high temperatures. This reaction can generate CaO, Ca3N2, CaCl2, respectively. At room temperature, it can react with water and the product is calcium hydroxide and hydrogen.
Calcium hydride has a strong reduction, and can make the metal liberate from the metal oxides, metal chlorides, for example,
2CaH2 + MO2→ 2CaO+2H2 + M (metal).
Calcium hydride can be used for strong reducing agent commonly, as well as used to make hydrogen when work in the field.
Preparation: The calcium metal is charged in the wok, and it can react with hydrogen to generate calcium hydride when temperature get about 300℃ with electric or oil.
Ca + H2 → CaH2 + 214kJ·mol-1
Or in a stream of hydrogen, magnesium can reduce calcium oxide reduction to get calcium hydride, due to the separation of calcium oxide is difficult, high purity calcium hydride products can not obtain.
CaO + Mg + H2 → CaH2 + MgO
Purpose: When be heated to 600 ~1000 ℃, the oxide of zirconium, niobium, uranium and chromium can be reduced to prepare powder of these metals, so calcium hydride can be used in powder metallurgy. It can be insoluble in ether, can react with ethanol to produce hydrogen and ethanol calcium. Hydrogen can be obtained by the reaction of water, one gram of the product in the water can release one liter of hydrogen, so it is often used as a portable source of hydrogen. In addition, calcium hydride is also used dehydration of organic compounds, hydrogenation, condensation agent; or as a drying agent, the drying effect is better than sodium, phosphorus pentoxide.
The above information is edited by the chemicalbook of Wang Xiaodong.








ToxicityWhen meet moisture, water or acids, hydrogen can be released and can cause combustion, it can react with oxidants and metal oxides violent. Dust can cause strong stimulating effect for the eyes, nose, skin and respiratory system. The product of calcium hydroxide is strong corrosive when meet moisture.
Other reference lithium hydride.
Chemical PropertiesIt is colorless orthorhombic crystallization; gray goods, orthorhombic or powder. It is sensitive to moisture. The relative density is 1.90. Melting point is 816℃ (in hydrogen). It can decompose to Ca and H2 at 600℃. With water it can decompose and release hydrogen at the same time, it can also generate hydrogen and ethanol calcium when react with ethanol. The reduction of metal oxides is more strongly than sodium hydride or lithium hydride.
UsesIt can be used as reducing agent and a condensing agent in organic synthesis, and desiccant in producing hydrogen material.
Production methodThe purity of about 99.5% purified calcium is put into the iron plate, then put on the central quartz reaction tube, at both ends of the quartz reaction tubes are installed into the trachea and a tube with rubber stopper, the purification of hydrogen go through from the intake pipe, the trachea is contact with by mineral oil bubbler and fume hood. The reaction tubes is electric heating. At beginning, raction air in the system is replaced by large purified hydrogen, then heated by an electric furnace. The reaction starts from about 200℃, further heated to 250~300℃, then a flow rate of 0.6 m 1/ min of hydrogen gas introduce into the reaction, the reaction needs about 2h to complete, the product of calcium hydride is porous white crystalline powder, the purity of calcium hydride is about 99%.
Ca + H2 → CaH2
CategoryExplosive substances.
Explosive hazardous characteristicsWhen the reaction was heated with tetrahydrofuran, it can cause explosion; when mix with potassium chlorate, hypochlorite, bromate, perchlorate, it is heat sensitive, friction sensitive and explosive.
Storage CharacteristicsTreasury need ventilation low temperature drying; shockproof, moistureproof, against high temperature.
Extinguishing agentFoam, carbon dioxide, dry powder.
DescriptionCalcium hydride is a gray powder (white if pure, which is rare). It reacts vigorously with water liberating H2 gas. CaH2 is thus used as a drying agent, i.e. a desiccant. It is prepared directly from the metal or by reacting CaCO3 with hydrogen at elevated temperatures. The overall reaction is shown as follows:
CaCO3+heat+H2→CaH2+H2O+CO2
CaH2 is a saline hydride, meaning that its structure is salt-like. The alkali metals and the alkaline earth metals all form saline hydrides. These species are insoluble in all solvents with which they do not react because they have extended structures. CaH2 crystallizes in the PbCl2 structural pattern.
The reaction of CaH2 with water can be represented as follows:
CaH2+2H2O0Ca(OH)2+2H2
The two hydrolysis products, H2, a gas, and Ca(OH)2, an aqueous mixture of solid plus liquid (i.e. a slurry), are readily separated from the solvent by distillation, filtration, or decantation.
Chemical Propertiesgreyish-white solid
Physical propertiesGrayish orthorhombic crystal or powder; stable at ambient temperature; density 1.70 g/cm3; melts at 816°C; reacts with water and alcohol.
UsesCalcium hydride is used as an efficient drying agent for aprotic base-stable solvents like ethers and tertiary amines. It is a useful dehydrating agent in a synthesis of aldehyde enamines in high yield and purity.
UsesCalcium hydride is a relatively mild desiccant. It is safer than the more reactive agents such as sodium metal. Calcium hydride is widely used as a desiccant for basic solvents such as amines and pyridine in organic syntheses. It is also used to pre-dry solvents prior to the use of a more reactive desiccant. The compound has, however, been widely used for decades as a safe and convenient means to inflate weather balloons. Likewise, it is regularly used in laboratories to produce small quantities of highly pure hydrogen for experiments.
UsesTo prepare rare metals by reduction of their oxides; as a drying agent for liquids and gases; to generate hydrogen: 1 g of calcium hydride in water liberates 1 liter of hydrogen at STP; in organic syntheses.
PreparationCalcium hydride may be prepared from its elements by direct combination of calcium and hydrogen at 300 to 400°C. It also can be made by heating calcium chloride with hydrogen in the presence of sodium metal:
CaCl2 + H2 + 2Na → CaH2 + NaCl
Alternatively, calcium hydride may be prepared by the reduction of calcium oxide with magnesium in the presence of hydrogen:
CaO + Mg + H2 → CaH2 + MgO.
Production MethodsCalcium hydride ignites in air on heating and can explode violently if mixed and rubbed with a strong oxidizing agent such as perchlorate or bromate. Contact with water produces hydrogen which can create a fire hazard in a confined space.
General DescriptionGrayish-colored lump or crystalline solid. Irritating to skin and eyes. Used to make other chemicals.
Air & Water ReactionsIgnites in air or reacts violently, sometimes explosively, with air of high humidity [Bretherick 1979 p. 107]. Reacts exothermically with water to generate flammable hydrogen gas and calcium hydroxide, a base. [Merck, 11th ed. 1989].
Reactivity ProfileWhen silver fluoride is ground with CALCIUM HYDRIDE the mass becomes incandescent [Mellor 3:389 1946-47]. Heating the hydride strongly with chlorine, bromine, or iodine leads to incandescence. Mixtures of the hydride with various bromates, i.e. barium bromate; chlorates, i.e. barium chlorate, and perchlorates, i.e. potassium perchlorate; explode on grinding, [Mellor, 1946, vol. 3, 651]. CaH2 reacts incandescently with AgF if subject to friction. (Mellor, 1941, Vol. 3, 389, 651).
HazardEvolves highly flammable hydrogen when wet; solid product is slaked lime. Irritating to skin.
Health HazardInhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.
Fire HazardProduce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard.
Flammability and ExplosibilityNotclassified
CALCIUM HYDRIDE CALCIUM BROMIDE HYDRATE Calcium phosphate monobasic ACID FUCHSIN CALCIUM SALT CALCIUM CARBONATE Ketoleucine calcium salt dihydrate Calcium chloride D-(+)-Pantothenic acid calcium salt Calcium nitrate BETA-NAPHTHYL ACID PHOSPHATE, CALCIUM SALT Calcium fluoride Calcium carbide DL-GLYCERIC ACID HEMICALCIUM SALT HYDRATE Calcium alpha-ketovaline 2-KETO-D-GLUCONIC ACID HEMICALCIUM SALT 3-METHYL-2-OXOPENTANOIC ACID CALCIUM Calcium hydroxide Phosphoric acid, calcium salt (1:?)

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