Magnesium silicide
2002029
218767635
2008-06-12T02:09:11Z
Hafap
7293733
{{Chembox new
| Name = Magnesium silicide
| ImageFile = Magnesium silicide.jpg
| ImageName = Magnesium silicide
| IUPACName = Magnesium silicide
| Section1 = {{Chembox Identifiers
| CASNo = 22831-39-6
}}
| Section2 = {{Chembox Properties
| Formula = Mg<sub>2</sub>Si
| MolarMass = 76.70 g mol<sup>−1</sup>
| Density = 2.56 g cm<sup>−3</sup>
| MeltingPt = 778 °C
| BoilingPt =
}}
| Section7 = {{Chembox Hazards
| NFPA-H = 2
| NFPA-F =
| NFPA-R =}}
}}
'''Magnesium silicide''', Mg<sub>2</sub>Si, is an [[inorganic compound]] consisting of [[magnesium]] and [[silicon]]. [[Silicon dioxide]], SiO<sub>2</sub>, found in [[sand]] and [[glass]], when heated with [[magnesium]] forms magnesium silicide. The first product in this reaction is [[silicon]], which then reacts further with magnesium to produce Mg<sub>2</sub>Si:
:SiO<sub>2</sub> + 2Mg → 2[[Magnesium oxide|MgO]] + Si
:Si + 2Mg → Mg<sub>2</sub>Si
Magnesium silicide is used to create aluminum alloys of the 6xxx group, containing up to approximately 1.5% Mg<sub>2</sub>Si. An alloy of this group can be age-hardened to form Guinier-Preston zones and a very fine precipitate, both resulting in increased strength of the alloy.<sup>[1]</sup>
When magnesium silicide is placed into [[hydrochloric acid]], HCl(aq), the gas [[silane]], SiH<sub>4</sub>, is produced. This gas is the silicon analogue of [[methane]], CH<sub>4</sub>, but is more reactive. Silane is [[Pyrophoricity|pyrophoric]], that is, due to the presence of [[oxygen]], it spontaneously combusts in air:
:Mg<sub>2</sub>Si(s) + 4HCl(aq) → SiH<sub>4</sub>(g) + 2MgCl<sub>2</sub>(s)
:SiH<sub>4</sub> + 2O<sub>2</sub> → SiO<sub>2</sub> + 2H<sub>2</sub>O
These reactions are typical of a [[Alkaline earth metal|Group 2]] [[silicide]]. Mg<sub>2</sub>Si reacts similarly with [[sulfuric acid]]. [[Alkali metal|Group 1]] silicides are even more reactive. For example, sodium silicide, Na<sub>2</sub>Si, reacts rapidly with water to yield [[sodium silicate]], Na<sub>2</sub>SiO<sub>3</sub>, and [[hydrogen]] gas.
==References==
[1] '''''ASM Handbook''''', 10th Ed., Vol. 1, '''''Properties and Selection: Non-ferrous Alloys and Special Purpose Materials''''', 1990, ASM International, Materials Park, Ohio.
<references/>
[[Category:Silicides]]
[[Category:Magnesium compounds]]
{{inorganic-compound-stub}}
[[ar:سيليسيد مغنزيوم]]