The formula of calcium bicarbonate is Ca(HCO₃)₂, also called calcium hydrogen carbonate. It exists only in solution form and is the primary cause of temporary hardness in water. When water containing CO₂ flows over limestone (CaCO₃), it dissolves it to form Ca(HCO₃)₂, which makes the water temporarily hard.
Calcium bicarbonate formula is Ca(HCO₃)₂ (calcium hydrogen carbonate).
Molar mass of Ca(HCO₃)₂ = 162.11 g/mol.
Ca(HCO₃)₂ exists only in aqueous solution, not as a pure solid.
It is the primary cause of temporary hardness in water.
Temporary hardness is removed by boiling: Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂.
Formation: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂ (limestone dissolving in CO₂-rich water).
Clark's process uses Ca(OH)₂ to remove temporary hardness by precipitating CaCO₃.
Limescale in kettles and boilers is CaCO₃ formed by decomposition of Ca(HCO₃)₂ on heating.
Chemical name: Calcium bicarbonate / Calcium hydrogen carbonate Molecular formula: Ca(HCO₃)₂ Molar mass: 162.11 g/mol
Ca(HCO₃)₂ is an ionic compound. The calcium ion Ca²⁺ is balanced by two bicarbonate (hydrogen carbonate) ions HCO₃⁻. It does not exist in solid form under normal conditions — attempts to isolate it as a solid cause it to decompose.
Calcium bicarbonate forms when carbon dioxide dissolved in water reacts with calcium carbonate (limestone):
CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂
This is how natural water becomes temporarily hard. Rainwater absorbs CO₂ from the atmosphere and soil, forming weak carbonic acid (H₂CO₃). This acid then dissolves limestone: CaCO₃ + H₂CO₃ → Ca(HCO₃)₂
Alternatively: CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂
The reverse reaction (decomposition) occurs upon heating.
Temporary hardness of water is caused by dissolved calcium bicarbonate Ca(HCO₃)₂ and magnesium bicarbonate Mg(HCO₃)₂. It is called 'temporary' because it can be removed by simply boiling the water:
Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂
On boiling, calcium bicarbonate decomposes back to insoluble calcium carbonate (which precipitates as scale/fur in kettles and boilers), water, and carbon dioxide gas. This removes the hardness.
Temporary hardness can also be removed by:
Temporary hardness:
Permanent hardness:
Total hardness = temporary hardness + permanent hardness Hardness is measured in ppm (parts per million) of CaCO₃ equivalent.
The formula of calcium bicarbonate (calcium hydrogen carbonate) is Ca(HCO₃)₂. It contains one Ca²⁺ ion and two HCO₃⁻ (bicarbonate) ions. Its molar mass is 162.11 g/mol.
Temporary hardness of water is caused by dissolved calcium bicarbonate Ca(HCO₃)₂ and magnesium bicarbonate Mg(HCO₃)₂. These form when CO₂-rich water dissolves limestone (CaCO₃) or magnesite.
Temporary hardness is removed by boiling: Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂. It can also be removed by Clark's process (adding lime Ca(OH)₂): Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃↓ + 2H₂O.
No, calcium bicarbonate Ca(HCO₃)₂ does not exist as a stable solid under normal conditions. It exists only in aqueous solution. When attempts are made to isolate it as a solid, it decomposes to CaCO₃, H₂O, and CO₂.
In nature, Ca(HCO₃)₂ forms when CO₂-rich rainwater reacts with limestone: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂. This dissolves limestone, creating caves, and makes groundwater temporarily hard. It also causes stalactite and stalagmite formation.
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