Question

Polyphosphates like sodium hexametaphosphate (calgon) 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 1

Answer: (C)

Form soluble complexes with cationic species

Answer 2

: Polyphosphates like sodium

hexametaphosphate (calgon) form soluble complexes with cations like $Ca^{2 +}$and $Mg^{2 +}$present in hard water.

$Na_{6}P_{6}O_{18} \rightarrow 2Na^{+} + Na_{6}P_{6}O_{18}^{2 -}$

$M^{2 +} + Na_{4}P_{6}O_{18} \rightarrow \lbrack Na_{2}MP_{6}O_{18}\rbrack^{2 -} + 2Na^{+}$