CaOH2

Calcium hydroxide, Ca(OH)2, also known as slaked lime or hydrated lime, is an inorganic compound that commonly appears as a white powder or granular solid. It is only sparingly soluble in water, and the dissolved portion forms a strong basic solution known as lime water.

Production and structure

Calcium hydroxide is produced industrially by reacting quicklime (CaO) with water: CaO + H2O → Ca(OH)2. This exothermic process yields a product that consists of calcium ions coordinated by hydroxide ions in a lattice. In water, the compound partially dissolves to give an alkaline solution with a typical pH around 12.4.

Properties

Ca(OH)2 has a molar mass of 74.09 g/mol. Its solubility in water at 20°C is about 1.7 g/L, making it only moderately soluble. The solid is white to grayish and has limited solubility in most organic solvents. Upon heating to decomposition temperatures above about 512°C, calcium hydroxide decomposes back to calcium oxide and water.

Uses

Calcium hydroxide is widely used in construction for lime mortars and plasters, agriculture to raise soil pH and supply calcium to plants, and water treatment to neutralize acidity and adjust alkalinity. It is also employed in flue gas desulfurization, the paper and pulp industry, and certain food-processing practices such as nixtamalization of maize.

Reactions

Ca(OH)2 readily neutralizes acids to form corresponding calcium salts. It reacts with carbon dioxide from the air to form calcium carbonate (CaCO3). It can also react with sulfurous or sulfate species under specific conditions.

Safety

Ca(OH)2 is caustic and can irritate skin and eyes. Inhalation of powder or dust should be avoided. Appropriate protective equipment is recommended when handling and applying the material.