Question
Polyphosphates are used as water softening agents because they
A.
form soluble complexes with anionic species
B.
precipitate anionic species
C.
form soluble complexes with cationic species
D.
precipitate cationic species
Answer :
form soluble complexes with cationic species
Solution :
$$2C{a^{2 + }} + N{a_2}\left[ {N{a_4}{{\left( {P{O_3}} \right)}_6}} \right] \to 4N{a^ + } + \mathop {N{a_2}\left[ {C{a_2}{{\left( {P{O_3}} \right)}_6}} \right]}\limits_{{\text{water}}\,{\text{soluble}}} $$