Question

Polyphosphates are used as water softening agents because they ______. 

Options

• form soluble complexes with anionic species

• precipitate anionic species

• form soluble complexes with cationic species

• precipitate cationic species

Answer 1

Polyphosphates are used as water softening agents because they form soluble complexes with cationic species.

Explanation:

With the \[\ce{Ca2+}\] and \[\ce{Mg2+}\] in hard water, polyphosphates (sodium hexametaphosphates, sodium tripolyphosphate, or STPP) form soluble complexes.