Soft water, Hard water & its Causes

Soft water, Hard water & its Causes

Soft water

 such a water which is not rich in minerals contents and can easily produces good lather (jhaag) with soap is called soft water.

Hard water

 such a water which is rich in minerals contents and cannot produce a good lather with soap is called hard water.

Causes of hardness of water

 When the rain water flows underground. It comes in contact with rocks. These rocks contain carbonates, sulphates and chloride of calcium and magnesium etc. which is soluble in water and water dissolves these common compounds. These salts when dissolve causes hardness of water. Carbon dioxide dissolves in water in from atmosphere which converts the carbonates of Ca and Mg into bicarbonates. As these bicarbonates are soluble in water causes hardness and are really dangerous. Such reactions are as follow   

CaCO₃   +   2H₂O   +   CO₂     è     Ca (HCO₃)₂

MgCO₃   +   2H₂O   +   CO₂     è     Mg (HCO₃)₂

Types of hard water

 The hardness of water is classified on the basis of types of minerals contents. Thus if mineral is easily removable is termed as temporary hardness or not easily removable is termed as permanent hardness. If water contains these minerals then it is termed as hardness of water. So there are two types of hard water. That is

• Temporary hard water       
• Permanent hard water

Temporary hard water

Such hardness of water which can easily be removed due to low mineral contents are called temporary hard water. This hardness of water is due to the presence of bicarbonates (HCO₃^–1) of Ca and Mg in water. These salts are soluble and present in form of ions. This hardness of water can be removed when it is warmed. The hardness will be removed. As when calcium carbonate is heated. It converts into insoluble carbonate. This insoluble carbonate settles down and simply decantation or filtration gives water free of this. 

                                 Ca (HCO₃)₂       è      CaCO₃   +    2H₂O   +   CO₂       

Mg (HCO₃)₂              è          MgCO₃   +    2H₂O   +   CO₂     

Permanent hard water

Such hardness of water which cannot be easily removed due to high mineral contents are called permanent hard water. This hardness of water is due to presence of chloride or

Sulphates of Ca and Mg. these salts are also soluble in water and produce corresponding ions in solution. This cannot be removed by heating like temporary hardness of water because become more soluble by heating but one complex method is available to remove this hardness that is ion exchange method etc.

 Such as

                     CaCl₂       +      H₂O       è       Ca⁺²        +      2Cl^–2 

                     MgSO₄    +       H₂O       è      Mg⁺²        +      SO₄^–2