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Polyphosphates are used as water softening agents because they

$\begin{array}{1 1}(a)\;\text{Form soluble complexes with anionic species}\\(b)\;\text{Precipitate anionic species}\\(c)\;\text{Form soluble complexes with cationic species}\\(d)\;\text{Precipitate cationic species}\end{array}$

1 Answer

Polyphosphates (sodium hexametaphosphates, sodium tripolyphosphate or STPP) from soluble complexes with $Ca^{+2}, Mg^{+2}$ present in hard water.
$2Ca^{2+}+Na_2[Na_4(PO_3)^6]\Rightarrow4Na^++Na_2[Ca_2(PO_2)_6]$
Form soluble complexes with cationic species
Hence (c) is the correct answer.
answered Jan 24, 2014 by sreemathi.v
edited Nov 23 by sharmaaparna1
 
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