2014-07-29

cause of hardness in natural waters

As ocean water evaporates, it form clouds, which condenses and precipitates rain.


As rain water falls it encounters carbon dioxide and reacts with it to form a mild acid (Carbonic Acid).

CO2 + H2O = H2CO3

Thus as rain water comes into contact with limestone in the earth, the limestone dissolves and goes into solution with the water.

CaCO3 + H2CO3 = Ca + 2 HCO3

Surface waters also encounter carbon dioxide from the decay of organic materials.
As these waters contact limestone, the limestone gradually dissolves and goes into solution.