Hard water is a type of water that contains a high concentration of minerals. When water percolates through deposits of limestone, chalk, or gypsum, hard water is produced. It is composed of bicarbonates of calcium, magnesium, and sulfates. Permanent hardness and temporary hardness are the two types of water hardness. Generally, the hardness of water is determined by complexometric tritration, titrating with a standard solution of the complexing agent ethylene diaminetetraacetic acid (EDTA).
The salt responsible for the permanent hardness of water is the presence of chlorides or sulphates of calcium or magnesium or both. The salt responsible for the temporary hardness of water is the presence of bicarbonates of calcium and magnesium or both.
| Permanent hardness of water is caused by | Temporary hardness of water is caused by |
|---|---|
| The presence of chlorides or sulphates of calcium or magnesium or both | The presence of bicarbonates of calcium and magnesium or both. |
Which salts are responsible for the hardness of water?
The salts responsible for water hardness are calcium, magnesium, and iron (II) ions. Generally, water contains naturally dissolved salts such as magnesium (Mg), calcium (Ca), chlorine (Cl), sodium (Na), iron (Fe), etc., and 55 percent of these are Ca and Mg, which are responsible for the hardness of the water.
What is the cause of the temporary hardness of water?
The presence of dissolved bicarbonate salts such as calcium bicarbonate (Ca (HCO3)3) and magnesium bicarbonate (Mg (HCO3)2) causes temporary hardness. These salts are composed of calcium and magnesium cations and bicarbonate and carbonate anions. The presence of these metal cations makes water hard.
What is the cause of the permanent hardness of water?
Permanent water hardness is caused by the presence of calcium chloride (CaCl2), calcium sulfate, magnesium chloride (MgCl2), and magnesium sulfate (MgSO4) in water, which do not precipitate when the temperature rises.
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