Alkali

An alkali is a chemical substance that produces an alkaline (basic) solution in water. In common usage, the term refers to soluble bases, especially the hydroxides of alkali metals. The classic examples are sodium hydroxide (NaOH) and potassium hydroxide (KOH). These substances dissociate in water to yield hydroxide ions (OH−), which raise the solution’s pH.

Alkali metals, the elements lithium, sodium, potassium, rubidium, cesium and francium, are the lightest and most reactive metals. Their hydroxides are highly soluble in water and form strongly basic solutions. When alkali metals contact water, they react vigorously, often with flammable hydrogen gas evolving: 2M + 2H2O → 2MOH + H2. The reactivity increases down the group, and the metals are stored under oil to prevent contact with moisture.

Alkalis occur in nature mainly as compounds rather than free metals. They are abundant in Earth’s crust and oceans in the form of salts and oxide/hydroxide minerals. They have important industrial roles, including in basic chemical processes and material production.

Uses and examples: NaOH and KOH are used in chemical manufacturing, soap making, paper production, and water treatment; sodium carbonate (washing soda) and other alkalies find use in glassmaking, detergents, and agriculture. Alkaline conditions are also maintained in many laboratory and industrial processes.

Safety: Alkalis are corrosive and can cause severe burns; they react with acids and moisture. They must be stored and handled with appropriate containment to prevent contact with skin and eyes.