pBlock ElementsII 1 Question 27
27. Polyphosphates are used as water softening agents because they
(2002, 3M)
(a) form soluble complexes with anionic species
(b) precipitate anionic species
(c) form soluble complexes with cationic species
(d) precipitate cationic species
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Answer:
Correct Answer: 27. (c)
Solution:
- Polyphosphates are used as water softening agents because they form soluble complexes with cationic species of hard water. $\mathrm{Na} _{2}\left[\mathrm{Na} _{4}\left(\mathrm{PO} _{3}\right) _{6}\right]+\mathrm{CaSO} _{4} \longrightarrow \underset{\text { Soluble complex }}{\mathrm{Na} _{2}\left[\left(\mathrm{Ca} _{2}\left(\mathrm{PO} _{3}\right) _{6}\right]+\mathrm{Na} _{2} \mathrm{SO} _{4}\right.}$
