Question

Permanent hardness of water can be removed by addition of which substance

Answer 1

HEYA...!!

Sodium carbonate, Na2CO3, is also known as washing soda. It can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble. The water is softenedbecause it no longer contains dissolved calcium ions and magnesium ions.

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Answer 2

Washing soda process 

In this process , hard water is treated with calculate amount of washing soda 

Na2CO3.10H2O 

CaCl2 + Na2CO3 → CaCO3↓ + 2 NaCl 

MgCl2 + Na2CO3 → MgCO3↓ + 2 NaCl

MgSO4 + Na2CO3 →MgCO3↓ + 2 NaSO4

Ion Exchange method 

Ion - inorganic cation exchangers 
(permuted process) 

Complex Inorganic salts like hydrated sodium , aluminum , silicates ( Na2 Al2 Si2 O8 . xH2O) have the interesting property of exchanging Ca2+ and Mg2+ ions present in the water with sodium present in complex salt 

CaCl2 + Na2Al2SiO8 → 2Nacl + CaAl2SiO8

MgCl2 + Na2Al2SiO8 → 2Nacl + MgAL2Si2O8 

It is efficient process 
It is very cheap process since during process only NaCl is consumed