Alkalis

Alkalis are bases that dissolve in water to form alkaline solutions. In aqueous solution, they release hydroxide ions (OH−), which give the solution its characteristic high pH. By definition, alkalis turn red litmus blue and neutralize acids to produce a corresponding salt and water. They are typically strong bases and often corrosive.

The most familiar alkalis are the soluble hydroxides of alkali metals such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH). Some alkaline earth metal hydroxides, notably calcium hydroxide (Ca(OH)2) and barium hydroxide (Ba(OH)2), also act as alkalis when dissolved, though their solubility varies. Ammonia dissolved in water forms ammonium hydroxide (NH4OH), a weak alkali.

Reactions involving alkalis include neutralization with acids: NaOH + HCl → NaCl + H2O. They also react with carbon dioxide in air or in solution to form carbonates: 2 NaOH + CO2 → Na2CO3 + H2O. Because of their caustic nature, alkalis are widely used in industry and household products: drain cleaners, soap making, paper chemistry, and pH control in water treatment.

Safety and handling are important, as alkalis can cause severe chemical burns and eye damage. Protective equipment should be used, and substances should be stored away from acids and incompatible materials. In summary, alkalis are water-soluble bases that generate alkaline solutions and participate in characteristic neutralization and buffering reactions.