Question

# Permanent hardness of water can be removed by Calgon method. If this is true enter 1, if false enter 0.

Hint: Adding Calgon to rough water results in sodium ions being separated from Calgon's anion. Now try to solve this using this hint.

Calgon is a trade name of a complex salt, sodium hexametaphosphate ${ ({ NaPO }_{ 3 }) }_{ 6 }$. It is used for softening hard water. Calgon ionizes to give a complex anion
The addition of Calgon to hard water causes the calcium and magnesium ions of hard water to displace sodium ions from the anion of Calgon.
From hard water Anion of calgon Goes into solution This results in the removal of calcium and magnesium ions from hard water in the form of a complex with Calgon.
${ 2CaCl }_{ 2 } + { Na }_{ 2 }[{ Na }_{ 4 }{ { ({ PO }_{ 3 }) }_{ 6 } }] \rightarrow { Na }_{ 2 }[{ Ca }_{ 2 }{ { ({ PO }_{ 3 }) }_{ 6 } }] + 4NaCl$

${ 2Mg }{ SO }_{ 4 } + { Na }_{ 2 }[{ Na }_{ 4 }{ { ({ PO }_{ 3 }) }_{ 6 } }] \rightarrow { Na }_{ 2 }[{ Mg }_{ 2 }{ { ({ PO }_{ 3 }) }_{ 6 } }] + { 2Na }_{ 2 }{ SO }_{ 4 }$
The water is softened and sodium ions are released into water.

This statement is True. Hence, the correct answer is 1.

Note: The complex calcium and Magnesium ions don't form any precipitate with soap and hence readily produce lather with soap. Because of its water-softening properties, people use Calgon products to remove and prevent hard water buildup in washing machines.