Calcium (Ca) and water
Calcium and water: reaction mechanisms, environmental impact and health effects
Calcium occurs in water naturally. Seawater contains approximately 400 ppm calcium. One of the main reasons for the abundance of calcium in water is its natural occurrence in the earth's crust. Calcium is also a constituent of coral. Rivers generally contain 1-2 ppm calcium, but in lime areas rivers may contains calcium concentrations as high as 100 ppm.
In what way and in what form does calcium react with water?
Ca (s) + 2H2O (g) -> Ca(OH)2 (aq) + H2 (g)
Other important calcium reaction mechanisms are erosion reactions. These usually occur when carbon dioxide is present. Under normal conditions calcium carbonate is water insoluble. When carbon dioxide is present carbonic acid is formed, affecting calcium compounds.
The reaction mechanism for carbon weathering is:
Solubility of calcium and calcium compounds
Why is calcium present in water?
Calcium is a dietary requirement for all organisms apart from some insects and bacteria. Calcium carbonate is a building stone of skeletons of most marine organisms, and eye lenses. Calcium phosphate is required for bone structure and teeth structure of terrestrial organisms. Plants mainly contain calcium oxalate. Calcium storage in plants is about 1% of dry mass.