Carbonite (ion)
Carbonite (CO32-) is a polyatomic anion composed of one carbon atom covalently bonded to three oxygen atoms. It carries a formal charge of -2. It is the conjugate base of the bicarbonate (hydrogen carbonate) ion (HCO3-), which is the conjugate base of carbonic acid (H2CO3).
Carbonite itself is generally unstable in aqueous solutions under standard conditions, readily protonating to form bicarbonate. Consequently, it is rarely encountered in significant concentrations in natural systems. Its presence is favored under highly alkaline conditions (high pH).
The carbonite ion plays a role in various chemical processes, including:
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Carbon cycle: While carbonite is not a major direct player in the carbon cycle, its existence is fundamentally linked to the equilibrium between carbon dioxide, carbonic acid, bicarbonate, and carbonate in aqueous environments.
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Buffering systems: The carbonate/bicarbonate system acts as a crucial buffer in biological systems and natural waters, helping to maintain a stable pH. Although the bicarbonate ion is more prevalent under physiological conditions, the underlying equilibrium includes the carbonite species.
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Mineral formation: Carbonite is a constituent of various carbonate minerals, such as calcite (calcium carbonate, CaCO3), aragonite (another polymorph of calcium carbonate), dolomite (calcium magnesium carbonate, CaMg(CO3)2), and siderite (iron carbonate, FeCO3). These minerals are found in sedimentary rocks, shells, and skeletons of marine organisms. The formation of these minerals involves the precipitation of metal cations with carbonite ions from solution.
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Industrial processes: Carbonite compounds are used in various industrial applications, including the production of cement, glass, and paper. They also play a role in the treatment of wastewater and the neutralization of acidic waste streams.
The stability of carbonite-containing compounds is greatly influenced by the identity of the associated cation, the pH, and the temperature.