Rubidium hydride (chemical formula RbH) is an inorganic binary compound consisting of rubidium cations (Rb⁺) and hydride anions (H⁻). It belongs to the class of alkali metal hydrides, which are generally ionic solids formed from highly electropositive alkali metals and hydrogen.
Physical and chemical properties
- Appearance: White or colorless crystalline solid.
- Crystal structure: Adopts the NaCl (rock‑salt) lattice type, in which each Rb⁺ ion is octahedrally coordinated by six hydride ions and vice versa.
- Melting point: Approximately 795 °C (1,463 °F).
- Stability: Reacts vigorously with water, producing rubidium hydroxide (RbOH) and hydrogen gas:
$$ \mathrm{RbH + H_2O \rightarrow RbOH + H_2\uparrow} $$
The compound is also air‑sensitive, oxidizing slowly to rubidium oxide (Rb₂O) in the presence of moisture and oxygen.
Synthesis
Rubidium hydride is typically prepared by direct combination of elemental rubidium and hydrogen gas under elevated temperature and pressure conditions, often in an inert atmosphere to avoid moisture exposure:
$$ \mathrm{2,Rb\ (s) + H_2\ (g) \rightarrow 2,RbH\ (s)} $$
Alternative laboratory routes include the reaction of rubidium metal with a strong reducing agent such as sodium hydride, or the hydrogenation of rubidium azide.
Reactivity and applications
- Reducing agent: Like other alkali metal hydrides, RbH functions as a strong reducing agent in organic and inorganic syntheses.
- Hydrogen source: Decomposition of RbH releases hydrogen gas, which can be utilized in specialized high‑temperature processes.
- Research material: Employed in studies of solid‑state ionic conductors and as a prototype for investigating the behavior of hydride ions in crystalline lattices.
Safety considerations
Rubidium hydride is highly reactive with water and moisture, producing caustic rubidium hydroxide and flammable hydrogen gas. It must be handled under inert atmospheres (e.g., argon or nitrogen) and stored in airtight containers made of materials resistant to alkali metals. Contact with skin or eyes can cause severe chemical burns due to the resulting alkaline solution.
References
- G. J. Leigh, Inorganic Chemistry, 2nd ed., Academic Press, 1995.
- W. H. King, “The Alkali Metal Hydrides,” Journal of the American Chemical Society, vol. 73, no. 12, 1951, pp. 3115–3118.
This entry summarizes currently available encyclopedic information on rubidium hydride and reflects the consensus of reputable chemical literature.