Introduction
Lithium hydroxide (LiOH) is an inorganic compound, specifically a salt, that is a white crystalline solid when anhydrous but often encountered as a monohydrate (LiOH⋅H2O). It consists of lithium cations (Li+) and hydroxide anions (OH-). LiOH is highly soluble in water and is commonly encountered as a solution.
Chemical Properties
As an ionic compound composed of lithium and hydroxide ions, LiOH shares many typical properties of salts. It dissolves readily in water to form an alkaline solution. When dissolved in water, LiOH ionizes into lithium cations and hydroxide anions according to the dissociation reaction:
LiOH (s) → Li+ (aq) + OH- (aq)
The resulting solutions are strongly alkaline, or basic, with a pH ranging from 11-12.5 depending on concentration. This solubility and basicity is indicative of the ionic character of the lithium-oxygen and hydrogen bonds in the solid. LiOH also has a high melting point of approximately 550°C, which reflects the strong electrostatic interactions between ions.
Uses and Applications
As an alkali metal hydroxide, LiOH has various industrial uses that exploit its strong basic nature. One major application is in lithium batteries, where it is used as an electrolyte. The high solubility of LiOH allows it to readily dissolve lithium salts and conduct lithium ions between the battery electrodes. LiOH is also used in the manufacture of lithium greases and as a desiccant to absorb water and carbon dioxide from air or gases.
In the glass industry, LiOH is added in small amounts to glass compositions. The lithium ions strengthen the glass by becoming part of the silicate network structure. Lithium-containing glasses have increased durability and improved chemical resistance. Pharmaceutical applications also exist, as LiOH is sometimes used as an ingredient in antacids and other medicines due to its alkalinizing properties.
Physical Properties
Beyond its chemical makeup and strong basicity in aqueous solution, LiOH has notable physical properties as well. As mentioned previously, its melting point is approximately 550°C, reflecting the strength of ionic bonding. Like other ionic compounds, it is generally hard and brittle in solid form. Anhydrous LiOH appears as white crystals or a powder, while the monohydrate exists as colorless crystals.
The density of LiOH is approximately 2.00 g/cm3. In terms of solubility, it exhibits high solubility in water, with a maximum solubility of 57g/100mL at 0°C. This enables it to act as a strong base when dissolved and essentially complete dissociation into its constituent ions. The highly soluble nature derives from the ability of waters’ polarity to strongly solvate both the lithium and hydroxide ions.
Environmental and Safety Considerations
Being a strong base, lithium hydroxide presents certain hazards if not properly handled or contained. Direct contact with concentrated solutions or solid LiOH can cause severe irritation and chemical burns to skin and eyes on contact. When heated, it may emit toxic fumes of lithium oxides. For these reasons, it is recommended to use protective equipment like gloves, eye protection, and respiratory masks when working with this compound.
Spills or releases of lithium hydroxide into the environment should also be avoided, as its high pH can raise the alkalinity of surrounding waters and soils. Solutions must be neutralized before disposal. However, as lithium is a relatively rare element, LiOH itself does not present significant environmental contamination concerns from a toxicity standpoint if carefully managed. Overall, through prudent handling and containment practices according to safety guidelines, LiOH can be utilized safely in industrial applications.
Conclusion
In summary, lithium hydroxide is an important industrial compound with applications spanning batteries, glass, pharmaceuticals and other areas. Its wide use stems from versatile chemical properties including high solubility, strong basicity in solution, and ability to conduct lithium ions effectively. Though presenting hazards from its caustic nature, LiOH can be employed safely in manufacturing when appropriate precautions and personal protective equipment are followed. A thorough understanding of its chemical makeup, physical attributes and environmental/safety considerations provides necessary background for its utilization.
