Question

write calgon's method for removal of permanent hardness of water

Answer 1

Calgon is a trade name of a complex salt, sodium hexametaphosphate (NaPO3)6. It is used for softening hard water. Calgon ionizes to give a complex anion

The addition of Calgon to hard water causes the calcium and magnesium ions of hard water to displace sodium ions from the anion of Calgon

Answer 2

In this process , Ca2+ and Mg2+ ions present in hard water arw rendered ineffective by treatment with sodium polymetaphosphate, ( NaPO3 ) x where x is as high as 100, or more commonly with sodium hexametaphosphate .
Na2[ Na 4 ( PO3 ) 6] .
The trade name for sodium hexametaphosphate is calgon ( Which means calcium gone )

When calgon is added to hard water , Ca2+ and Mg2+ ions present in it combine with sodium hexametaphosphate to form soluble complex of calcium and maganesium salts .

2CaCl2 + Na2[ Na4 ( PO3 )6] -------> Na2[Ca2(PO3)6] + 4NaCl

2MgSo4 + Na2[ Na4(PO3)6 ---------->
Na2[ Mg2(PO3)6] + 2Na2SO4

The complex calcium and Maganisum ions don't form any precipitate with soap and hence readily produced lather with soap.
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