HARD WATER
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"Water that produces curd with soap and produces very little lather
is called hard water. Hard water affects cleaning ability of soap."
   Hard water contains bicarbonate, chlorides and sulphates ( any one or all ) of calcium and magnesium .
SOFT WATER
 
"Water that produces lather with soap easily is called soft water.
Soft water does not affect cleaning action of soap"
TYPES OF HARD WATER
 
   There are two types of hard water.
   1. Temporary hard water
   2. Permanent hard water
TEMPORARY HARD WATER
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   "Water that contains bicarbonate of calcium and magnesium or of both is called temporary hard water."
   These bicarbonate are soluble in water and produce corresponding ions.
Mg(HCO3)2 è Mg+2 +2HCO3-1
Ca(HCO3)2 è Ca+2 + 2HCO3-1
PERMANENT HARD WATER
 
   Water that contains chlorides or sulphates of calcium or magnesium or of both is called Permanent water.
CaCl2è Ca+2 + 2Cl-1
MgSO4 è Mg+2 + SO4-2
   These compounds are soluble in water and produce corresponding ions.
REMOVAL OF HARDNESS OF WATER
 
   Hardness of water can be removed by the following two methods:
CLARK'S METHOD
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   In Clark’s method a calculated amount of calcium hydroxide Ca (OH)2 is added to hard water. Due to    reaction, insoluble carbonates are obtained which are separated by filtration.
Ca(HCO3)2 + Ca(OH)2 è 2CaCO3 + 2H2O
Mg(HCO3)2 + Ca(OH)2 è CaCO3 + MgCO3 + 2H2O
ION-EXCHANGE METHOD
 
   In this method sodium zeolite is used as ion-exchanger. Na-zeolite is passed through the pipes containing    hard water. Sodium zeolite is converted into calcium-zeolite or magnesium-zeolite. These are insoluble in    water and are separated from water by filtration.
Ca+2 + Na2-zeolite è Ca-zeolite + 2Na+1
Mg+2 +Na2-zeolite è Mg-zeolite + 2Na+1
DISADVANTAGE OF HARD WATER
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   Domestic:
   Hard water affect cleaning ability of soap.
   When hard water is used for washing, large amount of soap is consumed.
   Industrial:
   Hard water can cause "Scaling" inside the pipes that transport water . Therefore if we use hard water in    turbines and heat exchangers, their pipes will be corroded
   Health:
   Hard water when used for drinking for long period can lead to stomach disorders. Especially hard water    contains magnesium sulphate can weaken the stomach permanently.
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