Magnesium, reaction with water

Self-Test 14.6A Write the chemical equation for the reaction that would occur if you tried to put out a magnesium fire with water. 

The finely divided hydride produced by pyrolysis is pyrophoric in air, while synthesis from the elements produces a substantially air-stable product [1]. That prepared by reduction of butylmagnesium bromide with lithium tetrahydroalumi-nate is pyrophoric and reacts violently with water and other protic compounds [2], The hydride produced from magnesium anthracene has a very large specific surface area and is pyrophoric [3], In the context of use of the hydride for energy storage purposes, ignition and combustion behaviour of 100-400 g portions were studied, as well as the reaction with water [4],... 

As we shall see later, borides (as well as oxides, nitrides, carbides, etc.) react with water to produce a hydrogen compound of the nonmetal. Thus, the reaction of magnesium boride with water might be expected to produce BH3, borane, but instead the product is B2ff6, diborane (m.p. -165.5 °C, b.p. -92.5 °C). This interesting covalent hydride has the structure... 

The Grignard reaction is often one of the first reactions encountered for the preparation of organometallic compounds. As such it provides a method for the conversion of an alkyl bromide to an alkane. From the example shown below it is seen that the overall oxidation level change from the organic reactants to the products is from 0 to —2, so a reduction has occurred. Magnesium is the reductant and is itself oxidized from 0 to +2 oxidation state. The actual reduction takes place in the first step of the process in which the C-Br bond is converted to a C-Mg-Br bond. The reaction with water is merely a hydrolysis that does not change the oxidation state of carbon. 

Calcium, strontium, and barium react vigorously at 25°C. The less easily oxidized beryllium and magnesium show no observable reaction with water at 25°C, although magnesium reacts with boiling water. Table 18.7 summarizes various properties, sources, and preparations of the alkaline earth metals. 

ALUMINUM-MAGNESIUM ALLOY (12042-38-5) The dust or powder is a combustible solid it forms an explosive mixture in air. Violent reaction with water. A strong reducing agent. Incompatible with many materials, including oxidizers, strong acids, carbon tetrachloride, iron oxide, methyl chloroform, sodium nitrate. 

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