Calcium hydride

Calcium Hydride is a chemical compound with the formula CaH2. This grey powder (white when pure), which is a hard metal, is used as a drying agent for a wide range of solvents. It is also used in laboratories to produce hydrogen gas.

Chemical Properties

Calcium hydride is a binary compound of calcium and hydrogen. It is a grey or white powder when pure, with a high melting point of 816°C. It is a salt (ionic compound), being made up of calcium ions (Ca2+) and hydride ions (H−). The compound is thus an alkaline earth hydride. It reacts vigorously with water to form calcium hydroxide and hydrogen gas.

Production

Calcium hydride is produced industrially by heating lime (calcium oxide) with hydrogen in a high temperature furnace. The reaction is as follows:

CaO + H2 → CaH2 + H2O

The compound can also be produced by direct combination of calcium and hydrogen at temperatures between 300-400°C.

Uses

The main use of calcium hydride is as a drying agent in the preparation of certain solvents, such as ether and tetrahydrofuran. It can also be used to dry the air in a gas line to prevent condensation and the resulting corrosion. In laboratories, it is commonly used to produce small quantities of extremely pure hydrogen gas.

Safety

Calcium hydride is a highly reactive compound and should be handled with care. It reacts violently with water, releasing large amounts of heat and hydrogen gas, which can cause a fire or explosion. It should be stored in a cool, dry place, away from sources of moisture.

See Also

• Hydride
• Calcium
• Hydrogen