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CALCIUM HYDRIDE

Product Name:
CALCIUM HYDRIDE
CAS No.
7789-78-8
Chemical Name:
CALCIUM HYDRIDE
CBNumber:
CB0115234
Molecular Formula:
CaH2
Formula Weight:
42.09
MOL File:
7789-78-8.mol
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CALCIUM HYDRIDE Property

Melting point:
190 °C(lit.)
Density 
1.9
storage temp. 
Store at RT.
form 
powder
color 
Light gray
Specific Gravity
1.9
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.
InChIKey
FAQLAUHZSGTTLN-UHFFFAOYSA-N
CAS DataBase Reference
7789-78-8(CAS DataBase Reference)
NIST Chemistry Reference
calcium hydride(7789-78-8)
EPA Substance Registry System
Calcium hydride (CaH2) (7789-78-8)
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Safety

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
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N-Bromosuccinimide Price More Price(25)

Sigma-Aldrich Gold
Product number:
208027
Product name :
Calcium hydride
Purity:
reagent grade, 95% (gas-volumetric)
Packaging:
5g
Price:
$43
Updated:
2019/12/02
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Sigma-Aldrich Gold
Product number:
208027
Product name :
Calcium hydride
Purity:
reagent grade, 95% (gas-volumetric)
Packaging:
100g
Price:
$127
Updated:
2019/12/02
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Alfa Aesar Gold
Product number:
019106
Product name :
Calcium hydride, 90-95%
Packaging:
25g
Price:
$29.9
Updated:
2020/06/24
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Alfa Aesar Gold
Product number:
019106
Product name :
Calcium hydride, 90-95%
Packaging:
100g
Price:
$77.7
Updated:
2020/06/24
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Strem Chemicals Gold
Product number:
20-2021
Product name :
Calcium hydride, min. 97%
Packaging:
50g
Price:
$47
Updated:
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CALCIUM HYDRIDE Chemical Properties,Usage,Production

Alkaline earth metal

Calcium 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.

Toxicity

When 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 Properties

It 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.

Uses

It can be used as reducing agent and a condensing agent in organic synthesis, and desiccant in producing hydrogen material.

Production method

The 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

Category

Explosive substances.

Explosive hazardous characteristics

When 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 Characteristics

Treasury need ventilation low temperature drying; shockproof, moistureproof, against high temperature.

Extinguishing agent

Foam, carbon dioxide, dry powder.

Description

Calcium 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 Properties

greyish-white solid

Physical properties

Grayish orthorhombic crystal or powder; stable at ambient temperature; density 1.70 g/cm3; melts at 816°C; reacts with water and alcohol.

Uses

Calcium 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.

Uses

To 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.

Preparation

Calcium 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 Methods

Calcium 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 Description

Grayish-colored lump or crystalline solid. Irritating to skin and eyes. Used to make other chemicals.

Air & Water Reactions

Ignites 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 Profile

When 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).

Hazard

Evolves highly flammable hydrogen when wet; solid product is slaked lime. Irritating to skin.

Health Hazard

Inhalation 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 Hazard

Produce 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.

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Alkaline earth metal Toxicity Chemical Properties Uses Production method Category Explosive hazardous characteristics Storage Characteristics Extinguishing agent