The reagent which is not used for removing the permanent hardness of water is `:`

Options

A. washing soda
B. sodium hexametaphophate
C. Glauber's salt
D. hydrated sodium aluminium silicate ( zeolite )

Answer

3

Explanation

Permanenet hardness is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and sulphates in water.
`(1) MCl_(2)+Na_(2)CO_(3)rarrMCO_(3)darr+2NaCl`
`MSO_(4)+Na_(2)CO_(3)rarrMCO_(3)darr+Na_(2)SO_(4)`
`M=Ca,Mg`
`(2)` ` Na_(6)P_(6)O_(18)rarr2Na^(+)+Na_(4)P_(6)O_(18)^(-2)`
Complex anion keeps the `Mg^(2+)` and `Ca^(2+)` ions in solution.
`M^(2+)+Na_(4)P_(6)O_(18)^(2-)rarr[Na_(2)MP_(6)O_(18)]^(2-)+2Na^(+)`
`M=Ca,Mg`
`(3)` `Na_(2)SO_(4).10H_(2)O` is not used for removing the permanent hardness of water.
`(4)` `2NaZ(s)+M^(2+)(aq)rarrMZ_(2)(s)+2Na^(+)(aq) `
`M=Ca,Mg`