carbonatul

Carbonatul is the term used for the salts and esters of carbonic acid. The carbonate ion, CO3^2−, is the central structural unit of most carbonates, which occur widely in nature as minerals and rocks and are also synthesized for various industrial uses. The carbonate family includes numerous minerals such as calcite and aragonite (both forms of calcium carbonate, CaCO3), dolomite (CaMg(CO3)2), magnesite (MgCO3), siderite (FeCO3), smithsonite (ZnCO3), and cerussite (PbCO3). Carbonates are abundant in Earth’s crust and are important in geology, ore geology, and construction.

In aqueous systems, carbonate species arise from the acid–base equilibria of carbonic acid. Dissolved carbon dioxide forms carbonic acid, which dissociates to bicarbonate (HCO3−) and, at higher pH, to carbonate (CO3^2−). The distribution of these species depends on pH: CO2 and H2CO3 dominate at low pH, bicarbonate is prevalent around neutral to mildly alkaline conditions, and carbonate becomes dominant at high pH (above about pH 10). Carbonates readily react with acids, releasing carbon dioxide; for example, CaCO3 reacts with hydrochloric acid to form CaCl2, CO2, and H2O.

Industrial and practical relevance is broad. Limestone and marble (CaCO3) are quarried for construction, cement production, and agricultural lime. Sodium carbonate (Na2CO3) is a key chemical in glassmaking and the chemical industry. Thermal decomposition of carbonates yields oxides and CO2, a process central to cement manufacture and other high-temperature operations. Carbonates also contribute to environmental buffering in natural waters and to the biological formation of shells and skeletons in many marine organisms.