|Molar mass||124.94 g·mol−1|
|Appearance||white to red solid|
|Density||2.625 g cm−3|
|Melting point||875 °C (1,607 °F; 1,148 K)|
|reacts with water|
|105 J/mol K|
Std enthalpy of
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
This colourless solid is prepared by the reaction of selenium with a solution of sodium in liquid ammonia at -40 °C.
Alternatively, sodium selenide can be prepared by the reaction of gaseous hydrogen selenide with metallic sodium at 100 °C.
Like other alkali metal chalcogenides, this material is highly sensitive to water, easily undergoing hydrolysis to give mixtures of sodium biselenide (NaSeH) and hydroxide. This hydrolysis occurs because of the extreme basicity of the Se2− ion.
- Na2Se + H2O → NaHSe + NaOH
Similarly, sodium selenide is readily oxidized to polyselenides, a conversion signaled by off-white samples.
- Na2Se + 2 HCl → H2Se + 2 NaCl
The compound reacts with electrophiles to produce the selenium compounds. With alkyl halides, one obtains a variety of organoselenium compounds:
- Na2Se + 2 RBr → R2Se + 2 NaBr
- Na2Se + 2 Me3XCl → (Me3X)2Se + 2 NaCl (X ∈ Si, Ge, Sn)
Sodium selenide should be stored and handled away from moisture and air.
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