CaHCO

CaHCO, more formally known as calcium bicarbonate, is a chemical compound with the formula Ca(HCO3)2. It is an unstable salt formed from calcium ions (Ca2+) and bicarbonate ions (HCO3-). Calcium bicarbonate is highly soluble in water, which is a key characteristic contributing to its presence in natural water sources.

Unlike calcium carbonate (CaCO3), which is insoluble and forms limestone and chalk, calcium bicarbonate exists primarily in aqueous solution. It is often formed when water containing dissolved carbon dioxide (CO2) interacts with calcium carbonate. This process is fundamental to cave formation, where acidic water dissolves limestone, and can also contribute to the formation of scale in pipes and appliances if the water evaporates or its temperature changes, causing it to precipitate as calcium carbonate.

The presence of calcium bicarbonate in drinking water is what makes water "hard." Hard water can affect the lathering of soap and may leave mineral deposits. While not directly harmful to human health, the calcium and bicarbonate ions are dietary minerals. The instability of calcium bicarbonate means it readily decomposes upon heating or exposure to air, reverting to calcium carbonate, water, and carbon dioxide. This reversibility is important in geological and environmental processes.