Calcium carbonate, water, and carbon dioxide react to produce calcium bicarbonate.
Understanding the Reaction
The reaction is a chemical process where solid calcium carbonate (CaCO3) dissolves in water (H2O) containing dissolved carbon dioxide (CO2). This reaction results in the formation of aqueous calcium bicarbonate (Ca(HCO3)2).
The balanced chemical equation for this reaction is:
CaCO3 (s) + H2O (l) + CO2 (g) → Ca(HCO3)2 (aq)
- CaCO3 (s): Calcium carbonate in its solid form (e.g., limestone, chalk).
- H2O (l): Water in its liquid form.
- CO2 (g): Carbon dioxide in its gaseous form.
- Ca(HCO3)2 (aq): Calcium bicarbonate dissolved in water (aqueous solution).
Significance of the Reaction
This reaction is crucial in various natural processes:
- Cave Formation: Rainwater absorbs carbon dioxide from the atmosphere and soil, becoming slightly acidic. As this acidic water percolates through limestone (calcium carbonate) rock, it dissolves the calcium carbonate, forming calcium bicarbonate. This dissolved calcium bicarbonate is then carried away, contributing to the formation of caves and other karst landscapes.
- Hard Water: Calcium bicarbonate contributes to the hardness of water. When water containing calcium bicarbonate is heated, the reverse reaction occurs, precipitating calcium carbonate as scale (e.g., in kettles and pipes).
Example
Imagine rainwater seeping through limestone bedrock. The rainwater, containing dissolved carbon dioxide, reacts with the calcium carbonate in the limestone. Over time, this process dissolves the limestone, widening cracks and fissures, and eventually leading to the formation of underground cave systems. The dissolved calcium carbonate is now in the form of calcium bicarbonate, carried along in the water.
