Chemical Property of Calcium hydride (CaH2)
Chemical Property:
- Appearance/Colour:greyish-white solid
- Melting Point:190 °C(lit.)
- Boiling Point:1484oC
- PSA：0.00000
- Density:1.9
- LogP:0.22500
- Storage Temp.:Store at RT.
- Sensitive.:Moisture Sensitive
- Water Solubility.:Soluble in water and alcohol. Insoluble in benzene.
- Hydrogen Bond Donor Count:0
- Hydrogen Bond Acceptor Count:2
- Rotatable Bond Count:0
- Exact Mass:41.9782409
- Heavy Atom Count:1
- Complexity:0
- Purity/Quality:
-
99% *data from raw suppliers
Calcium hydride *data from reagent suppliers
Safty Information:
- Pictogram(s):
F
- Hazard Codes:F
- Statements:
15
- Safety Statements:
24/25-43-7/8-43A
- MSDS Files:
-
SDS file from LookChem
Total 1 MSDS from other Authors
Useful:
- Canonical SMILES:[H-].[H-].[Ca+2]
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Uses
It can be used as reducing agent and a condensing agent in organic synthesis, and desiccant in producing hydrogen material. Calcium 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. 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. 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.
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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
-
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.
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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.
