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]]