The Reagent which is commercially known as ‘calgon’ that is used to remove the permanent hardness of water in Calgon’s method. Find out the number of moles of calgon required to remove 12 moles of `Ca^(2+)` ion present in hard water.

Answer

4

Explanation

Sodium hexametaphosphate `[Na_(6)P_(6)O_(18)]` is known as calgon. When it is added to hard water the following reaction takes place.
`Na_(6)P_(6)P_(18)to 6Na^(+)+P_(6)O_(18)^(6-)`
`3Ca^(2+)+N_(6)P_(6)O_(18)to 6 Na^(+)+Ca_(3)P_(6)O_(18)`
`{:("3 mole","1 mole"),("12 mole","4 mole"):}`